Table des matières

Command Line Interface

Dernière mise-à-jour : 2020/01/30 03:28

Command Line Interface

The Shell

A shell is a Command Line Interpreter (C.L.I). It is used to give instructions or commands to the operating system (OS).

The word shell is generic. There are many shells under Unix and Linux such as:

Shell	Name	Release Date	Inventer	Command	Comments
tsh	Thompson Shell	1971	Ken Thompson	sh	The first shell
sh	Bourne Shell	1977	Stephen Bourne	sh	The shell common to all Unix and Linux OSs: /bin/sh
csh	C-Shell	1978	Bill Joy	csh	The BSD shell: /bin/csh
tcsh	Tenex C-Shell	1979	Ken Greer	tcsh	A fork of the csh shell: /bin/tcsh
ksh	Korn Shell	1980	David Korn	ksh	Open Source since 2005: /bin/ksh
bash	Bourne Again Shell	1987	Brian Fox	bash	The default shell for Linux, MacOS X, Solaris 11: /bin/bash
zsh	Z Shell	1990	Paul Falstad	zsh	Zsh is an extended Bourne shell with a large number of improvements, including some features of bash, ksh, and tcsh: /usr/bin/zsh

When using Debian 8 /bin/sh is a soft link to /bin/dash :

trainee@debian8:~$ ls -l /bin/sh
lrwxrwxrwx 1 root root 4 Nov  8  2014 /bin/sh -> dash

When using Ubuntu 16.04 /bin/sh is a soft link to /bin/dash :

trainee@ubuntu1604:~$ ls -l /bin/sh
lrwxrwxrwx 1 root root 4 mai    3  2016 /bin/sh -> dash

When using RHEL/CentOS 7 /bin/sh is a soft link to /bin/bash :

[trainee@centos7 ~]$ ls -l /bin/sh
lrwxrwxrwx. 1 root root 4 30 sept. 06:01 /bin/sh -> bash

When using SLES 12 /bin/sh is a soft link to /bin/bash :

trainee@SLES12SP1:~> ls -l /bin/sh
lrwxrwxrwx 1 root root 4  1 mai    2016 /bin/sh -> bash

/bin/bash

This unit covers the /bin/bash shell. The /bin/bash shell allows you to:

Recall previously typed commands
Auto-generate the end of a file name
Use Aliases
Use tables
Use C language numerical and math variables
Manage strings
Use Functions

A command always starts with a keyword. This keyword is interpreted by the shell, in the order shown, as one of the following:

An Alias,
A Function,
A Built-in Command,
An External Command.

Internal And External Commands

The /bin/bash shell comes with a set of built-in or internal commands. External commands are executable binaries or scripts generally found in one of the following directories:

/bin,
/sbin,
/usr/bin,
/usr/sbin.

To check if a command is internal to the shell or external, use the type command:

trainee@debian8:~$ type cd
cd is a shell builtin

trainee@ubuntu1604:~$ type cd
cd is a shell builtin

[trainee@centos7 ~]$ type cd
cd is a shell builtin

trainee@SLES12SP1:~> type cd
cd is a shell builtin

External commands are either binaries or scripts that can be found in /bin, /sbin, /usr/bin or /usr/sbin :

trainee@debian8:~$ type passwd
passwd is /usr/bin/passwd

trainee@ubuntu1604:~$ type passwd
passwd is /usr/bin/passwd

[trainee@centos7 ~]$ type passwd
passwd is /usr/bin/passwd

trainee@SLES12SP1:~> type passwd
passwd is /usr/bin/passwd

Aliases

Aliases are strings that are aliased to a command, a command and some options or even several commands. Aliases are specific to the shell in which they are created and unless specified in one of the start-up files, they disappear when the shell is closed:

trainee@debian8:~$ type ls
ls is aliased to `ls --color=auto

trainee@ubuntu1604:~$ type ls
ls is aliased to `ls --color=auto'

[trainee@centos7 ~]$ type ls
ls is aliased to `ls --color=auto'

trainee@SLES12SP1:~> type ls
ls is aliased to `_ls'

Important: Note that the ls alias is an alias to the ls command itself.

An alias is defined using the alias command:

trainee@debian8:~$ alias dir='ls -l'
trainee@debian8:~$ dir
total 36
-rw-r--r-- 1 trainee trainee    0 Aug 19 17:08 aac
-rw-r--r-- 1 trainee trainee    0 Aug 19 17:08 abc
-rw-r--r-- 1 trainee trainee    0 Aug 19 17:08 bca
drwxr-xr-x 2 trainee trainee 4096 May  1  2016 Desktop
drwxr-xr-x 2 trainee trainee 4096 May  1  2016 Documents
drwxr-xr-x 2 trainee trainee 4096 May  1  2016 Downloads
drwxr-xr-x 2 trainee trainee 4096 May  1  2016 Music
drwxr-xr-x 2 trainee trainee 4096 May  1  2016 Pictures
drwxr-xr-x 2 trainee trainee 4096 May  1  2016 Public
drwxr-xr-x 2 trainee trainee 4096 May  1  2016 Templates
drwxr-xr-x 2 trainee trainee 4096 May  1  2016 Videos
-rw-r--r-- 1 trainee trainee  391 Aug 18 23:34 vitext
-rw-r--r-- 1 trainee trainee    0 Aug 19 17:08 xyz

trainee@ubuntu1604:~$ alias dir='ls -l'
trainee@ubuntu1604:~$ dir
total 48
-rw-rw-r-- 1 trainee trainee    0 oct.   4 14:24 aac
-rw-rw-r-- 1 trainee trainee    0 oct.   4 14:24 abc
-rw-rw-r-- 1 trainee trainee    0 oct.   4 14:24 bca
drwxr-xr-x 2 trainee trainee 4096 mai    3  2016 Desktop
drwxr-xr-x 2 trainee trainee 4096 mai    3  2016 Documents
drwxr-xr-x 2 trainee trainee 4096 mai    3  2016 Downloads
-rw-r--r-- 1 trainee trainee 8980 mai    3  2016 examples.desktop
drwxr-xr-x 2 trainee trainee 4096 mai    3  2016 Music
drwxr-xr-x 2 trainee trainee 4096 mai    3  2016 Pictures
drwxr-xr-x 2 trainee trainee 4096 mai    3  2016 Public
drwxr-xr-x 2 trainee trainee 4096 mai    3  2016 Templates
drwxr-xr-x 2 trainee trainee 4096 mai    3  2016 Videos
-rw-rw-r-- 1 trainee trainee  442 sept. 30 11:35 vitext
-rw-rw-r-- 1 trainee trainee    0 oct.   4 14:24 xyz

[trainee@centos7 ~]$ alias dir='ls -l'
[trainee@centos7 ~]$ dir
total 4
-rw-rw-r--. 1 trainee trainee   0 29 sept. 18:20 aac
-rw-rw-r--. 1 trainee trainee   0 29 sept. 18:20 abc
-rw-rw-r--. 1 trainee trainee   0 29 sept. 18:20 bca
drwxr-xr-x. 2 trainee trainee   6 30 avril 11:54 Desktop
drwxr-xr-x. 2 trainee trainee   6 30 avril 11:54 Documents
drwxr-xr-x. 2 trainee trainee   6 30 avril 11:54 Downloads
drwxr-xr-x. 2 trainee trainee   6 30 avril 11:54 Music
drwxr-xr-x. 2 trainee trainee   6 30 avril 11:54 Pictures
drwxr-xr-x. 2 trainee trainee   6 30 avril 11:54 Public
drwxr-xr-x. 2 trainee trainee   6 30 avril 11:54 Templates
drwxr-xr-x. 2 trainee trainee   6 30 avril 11:54 Videos
-rw-rw-r--. 1 trainee trainee 442 29 sept. 00:53 vitext
-rw-rw-r--. 1 trainee trainee   0 29 sept. 18:20 xyz

trainee@SLES12SP1:~> alias dir='ls -l'
trainee@SLES12SP1:~> dir
total 4
-rw-r--r-- 1 trainee users   0  1 oct.  06:55 aac
-rw-r--r-- 1 trainee users   0  1 oct.  06:55 abc
-rw-r--r-- 1 trainee users   0  1 oct.  06:55 bca
drwxr-xr-x 1 trainee users   0  1 mai    2016 bin
drwxr-xr-x 1 trainee users   0  2 mai    2016 Desktop
drwxr-xr-x 1 trainee users   0  2 mai    2016 Documents
drwxr-xr-x 1 trainee users   0  2 mai    2016 Downloads
drwxr-xr-x 1 trainee users   0  2 mai    2016 Music
drwxr-xr-x 1 trainee users   0  2 mai    2016 Pictures
drwxr-xr-x 1 trainee users   0  2 mai    2016 Public
drwxr-xr-x 1 trainee users  20  1 mai    2016 public_html
drwxr-xr-x 1 trainee users   0  2 mai    2016 Templates
drwxr-xr-x 1 trainee users   0  2 mai    2016 Videos
-rw-r--r-- 1 trainee users 391 30 sept. 10:27 vitext
-rw-r--r-- 1 trainee users   0  1 oct.  06:55 xyz

Important: Note that dir exists as a command. By creating an alias of the same name, the alias will be executed in place of the command.

The list of currently defined aliases is obtained by using the alias command with no options:

trainee@debian8:~$ alias
alias dir='ls -l'
alias ls='ls --color=auto'

trainee@ubuntu1604:~$ alias
alias alert='notify-send --urgency=low -i "$([ $? = 0 ] && echo terminal || echo error)" "$(history|tail -n1|sed -e '\''s/^\s*[0-9]\+\s*//;s/[;&|]\s*alert$//'\'')"'
alias dir='ls -l'
alias egrep='egrep --color=auto'
alias fgrep='fgrep --color=auto'
alias grep='grep --color=auto'
alias l='ls -CF'
alias la='ls -A'
alias ll='ls -alF'
alias ls='ls --color=auto'

[trainee@centos7 ~]$ alias
alias dir='ls -l'
alias egrep='egrep --color=auto'
alias fgrep='fgrep --color=auto'
alias grep='grep --color=auto'
alias l.='ls -d .* --color=auto'
alias ll='ls -l --color=auto'
alias ls='ls --color=auto'
alias vi='vim'
alias which='alias | /usr/bin/which --tty-only --read-alias --show-dot --show-tilde'

trainee@SLES12SP1:~> alias
alias +='pushd .'
alias -='popd'
alias ..='cd ..'
alias ...='cd ../..'
alias aumix='padsp aumix'
alias beep='echo -en "\007"'
alias cd..='cd ..'
alias dir='ls -l'
alias egrep='egrep --color=auto'
alias fgrep='fgrep --color=auto'
alias grep='grep --color=auto'
alias l='ls -alF'
alias la='ls -la'
alias ll='ls -l'
alias ls='_ls'
alias ls-l='ls -l'
alias md='mkdir -p'
alias o='less'
alias rd='rmdir'
alias rehash='hash -r'
alias sox='padsp sox'
alias timidity='timidity -Oe'
alias unmount='echo "Error: Try the command: umount" 1>&2; false'
alias you='if test "$EUID" = 0 ; then /sbin/yast2 online_update ; else su - -c "/sbin/yast2 online_update" ; fi'

Important: In the above list you can see, without distinction, the system wide aliases created by system start up scripts and the user created alias dir. The latter is only available for trainee and will disappear when the current session is terminated.

To force the shell to use the command and not the alias, you can precede the command with the \ character:

trainee@debian8:~$ \dir
aac  bca      Documents  Music	   Public     Videos  xyz
abc  Desktop  Downloads  Pictures  Templates  vitext

trainee@ubuntu1604:~$ \dir
aac  bca      Documents  examples.desktop  Pictures  Templates	vitext
abc  Desktop  Downloads  Music		   Public    Videos	xyz

[trainee@centos7 ~]$ \dir
aac  bca      Documents  Music	   Public     Videos  xyz
abc  Desktop  Downloads  Pictures  Templates  vitext

trainee@SLES12SP1:~> \dir
aac  bca  Desktop    Downloads	Pictures  public_html  Videos  xyz
abc  bin  Documents  Music	Public	  Templates    vitext

To delete an alias, simply use the unalias command:

trainee@debian8:~$ unalias dir
trainee@debian8:~$ dir
aac  bca      Documents  Music	   Public     Videos  xyz
abc  Desktop  Downloads  Pictures  Templates  vitext

trainee@ubuntu1604:~$ unalias dir
trainee@ubuntu1604:~$ dir
aac  bca      Documents  examples.desktop  Pictures  Templates	vitext
abc  Desktop  Downloads  Music		   Public    Videos	xyz

[trainee@centos7 ~]$ unalias dir
[trainee@centos7 ~]$ dir
aac  bca      Documents  Music	   Public     Videos  xyz
abc  Desktop  Downloads  Pictures  Templates  vitext

trainee@SLES12SP1:~> unalias dir
trainee@SLES12SP1:~> dir
aac  bca  Desktop    Downloads	Pictures  public_html  Videos  xyz
abc  bin  Documents  Music	Public	  Templates    vitext

Each user's shell is defined by root in the /etc/passwd file:

trainee@debian8:~$ cat /etc/passwd
root:x:0:0:root:/root:/bin/bash
daemon:x:1:1:daemon:/usr/sbin:/usr/sbin/nologin
bin:x:2:2:bin:/bin:/usr/sbin/nologin
sys:x:3:3:sys:/dev:/usr/sbin/nologin
sync:x:4:65534:sync:/bin:/bin/sync
games:x:5:60:games:/usr/games:/usr/sbin/nologin
man:x:6:12:man:/var/cache/man:/usr/sbin/nologin
lp:x:7:7:lp:/var/spool/lpd:/usr/sbin/nologin
mail:x:8:8:mail:/var/mail:/usr/sbin/nologin
news:x:9:9:news:/var/spool/news:/usr/sbin/nologin
uucp:x:10:10:uucp:/var/spool/uucp:/usr/sbin/nologin
proxy:x:13:13:proxy:/bin:/usr/sbin/nologin
www-data:x:33:33:www-data:/var/www:/usr/sbin/nologin
backup:x:34:34:backup:/var/backups:/usr/sbin/nologin
list:x:38:38:Mailing List Manager:/var/list:/usr/sbin/nologin
irc:x:39:39:ircd:/var/run/ircd:/usr/sbin/nologin
gnats:x:41:41:Gnats Bug-Reporting System (admin):/var/lib/gnats:/usr/sbin/nologin
nobody:x:65534:65534:nobody:/nonexistent:/usr/sbin/nologin
systemd-timesync:x:100:103:systemd Time Synchronization,,,:/run/systemd:/bin/false
systemd-network:x:101:104:systemd Network Management,,,:/run/systemd/netif:/bin/false
systemd-resolve:x:102:105:systemd Resolver,,,:/run/systemd/resolve:/bin/false
systemd-bus-proxy:x:103:106:systemd Bus Proxy,,,:/run/systemd:/bin/false
trainee:x:1000:1000:trainee,,,:/home/trainee:/bin/bash
sshd:x:104:65534::/var/run/sshd:/usr/sbin/nologin
Debian-exim:x:105:110::/var/spool/exim4:/bin/false
messagebus:x:106:111::/var/run/dbus:/bin/false
statd:x:107:65534::/var/lib/nfs:/bin/false
avahi-autoipd:x:108:113:Avahi autoip daemon,,,:/var/lib/avahi-autoipd:/bin/false
avahi:x:109:115:Avahi mDNS daemon,,,:/var/run/avahi-daemon:/bin/false
colord:x:110:117:colord colour management daemon,,,:/var/lib/colord:/bin/false
dnsmasq:x:111:65534:dnsmasq,,,:/var/lib/misc:/bin/false
speech-dispatcher:x:112:29:Speech Dispatcher,,,:/var/run/speech-dispatcher:/bin/sh
pulse:x:113:119:PulseAudio daemon,,,:/var/run/pulse:/bin/false
rtkit:x:114:121:RealtimeKit,,,:/proc:/bin/false
saned:x:115:122::/var/lib/saned:/bin/false
usbmux:x:116:46:usbmux daemon,,,:/var/lib/usbmux:/bin/false
lightdm:x:117:124:Light Display Manager:/var/lib/lightdm:/bin/false

trainee@ubuntu1604:~$ cat /etc/passwd
root:x:0:0:root:/root:/bin/bash
daemon:x:1:1:daemon:/usr/sbin:/usr/sbin/nologin
bin:x:2:2:bin:/bin:/usr/sbin/nologin
sys:x:3:3:sys:/dev:/usr/sbin/nologin
sync:x:4:65534:sync:/bin:/bin/sync
games:x:5:60:games:/usr/games:/usr/sbin/nologin
man:x:6:12:man:/var/cache/man:/usr/sbin/nologin
lp:x:7:7:lp:/var/spool/lpd:/usr/sbin/nologin
mail:x:8:8:mail:/var/mail:/usr/sbin/nologin
news:x:9:9:news:/var/spool/news:/usr/sbin/nologin
uucp:x:10:10:uucp:/var/spool/uucp:/usr/sbin/nologin
proxy:x:13:13:proxy:/bin:/usr/sbin/nologin
www-data:x:33:33:www-data:/var/www:/usr/sbin/nologin
backup:x:34:34:backup:/var/backups:/usr/sbin/nologin
list:x:38:38:Mailing List Manager:/var/list:/usr/sbin/nologin
irc:x:39:39:ircd:/var/run/ircd:/usr/sbin/nologin
gnats:x:41:41:Gnats Bug-Reporting System (admin):/var/lib/gnats:/usr/sbin/nologin
nobody:x:65534:65534:nobody:/nonexistent:/usr/sbin/nologin
systemd-timesync:x:100:102:systemd Time Synchronization,,,:/run/systemd:/bin/false
systemd-network:x:101:103:systemd Network Management,,,:/run/systemd/netif:/bin/false
systemd-resolve:x:102:104:systemd Resolver,,,:/run/systemd/resolve:/bin/false
systemd-bus-proxy:x:103:105:systemd Bus Proxy,,,:/run/systemd:/bin/false
syslog:x:104:108::/home/syslog:/bin/false
_apt:x:105:65534::/nonexistent:/bin/false
messagebus:x:106:110::/var/run/dbus:/bin/false
uuidd:x:107:111::/run/uuidd:/bin/false
lightdm:x:108:114:Light Display Manager:/var/lib/lightdm:/bin/false
whoopsie:x:109:116::/nonexistent:/bin/false
avahi-autoipd:x:110:119:Avahi autoip daemon,,,:/var/lib/avahi-autoipd:/bin/false
avahi:x:111:120:Avahi mDNS daemon,,,:/var/run/avahi-daemon:/bin/false
dnsmasq:x:112:65534:dnsmasq,,,:/var/lib/misc:/bin/false
colord:x:113:123:colord colour management daemon,,,:/var/lib/colord:/bin/false
speech-dispatcher:x:114:29:Speech Dispatcher,,,:/var/run/speech-dispatcher:/bin/false
hplip:x:115:7:HPLIP system user,,,:/var/run/hplip:/bin/false
kernoops:x:116:65534:Kernel Oops Tracking Daemon,,,:/:/bin/false
pulse:x:117:124:PulseAudio daemon,,,:/var/run/pulse:/bin/false
rtkit:x:118:126:RealtimeKit,,,:/proc:/bin/false
saned:x:119:127::/var/lib/saned:/bin/false
usbmux:x:120:46:usbmux daemon,,,:/var/lib/usbmux:/bin/false
trainee:x:1000:1000:trainee,,,:/home/trainee:/bin/bash
sshd:x:121:65534::/var/run/sshd:/usr/sbin/nologin

[trainee@centos7 ~]$ cat /etc/passwd
root:x:0:0:root:/root:/bin/bash
bin:x:1:1:bin:/bin:/sbin/nologin
daemon:x:2:2:daemon:/sbin:/sbin/nologin
adm:x:3:4:adm:/var/adm:/sbin/nologin
lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin
sync:x:5:0:sync:/sbin:/bin/sync
shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown
halt:x:7:0:halt:/sbin:/sbin/halt
mail:x:8:12:mail:/var/spool/mail:/sbin/nologin
operator:x:11:0:operator:/root:/sbin/nologin
games:x:12:100:games:/usr/games:/sbin/nologin
ftp:x:14:50:FTP User:/var/ftp:/sbin/nologin
nobody:x:99:99:Nobody:/:/sbin/nologin
avahi-autoipd:x:170:170:Avahi IPv4LL Stack:/var/lib/avahi-autoipd:/sbin/nologin
systemd-bus-proxy:x:999:997:systemd Bus Proxy:/:/sbin/nologin
systemd-network:x:998:996:systemd Network Management:/:/sbin/nologin
dbus:x:81:81:System message bus:/:/sbin/nologin
polkitd:x:997:995:User for polkitd:/:/sbin/nologin
abrt:x:173:173::/etc/abrt:/sbin/nologin
usbmuxd:x:113:113:usbmuxd user:/:/sbin/nologin
colord:x:996:993:User for colord:/var/lib/colord:/sbin/nologin
libstoragemgmt:x:995:992:daemon account for libstoragemgmt:/var/run/lsm:/sbin/nologin
setroubleshoot:x:994:991::/var/lib/setroubleshoot:/sbin/nologin
rpc:x:32:32:Rpcbind Daemon:/var/lib/rpcbind:/sbin/nologin
rtkit:x:172:172:RealtimeKit:/proc:/sbin/nologin
chrony:x:993:990::/var/lib/chrony:/sbin/nologin
unbound:x:992:989:Unbound DNS resolver:/etc/unbound:/sbin/nologin
tss:x:59:59:Account used by the trousers package to sandbox the tcsd daemon:/dev/null:/sbin/nologin
geoclue:x:991:988:User for geoclue:/var/lib/geoclue:/sbin/nologin
ntp:x:38:38::/etc/ntp:/sbin/nologin
sssd:x:990:987:User for sssd:/:/sbin/nologin
rpcuser:x:29:29:RPC Service User:/var/lib/nfs:/sbin/nologin
nfsnobody:x:65534:65534:Anonymous NFS User:/var/lib/nfs:/sbin/nologin
pulse:x:171:171:PulseAudio System Daemon:/var/run/pulse:/sbin/nologin
gdm:x:42:42::/var/lib/gdm:/sbin/nologin
gnome-initial-setup:x:989:984::/run/gnome-initial-setup/:/sbin/nologin
avahi:x:70:70:Avahi mDNS/DNS-SD Stack:/var/run/avahi-daemon:/sbin/nologin
postfix:x:89:89::/var/spool/postfix:/sbin/nologin
sshd:x:74:74:Privilege-separated SSH:/var/empty/sshd:/sbin/nologin
tcpdump:x:72:72::/:/sbin/nologin
trainee:x:1000:1000:trainee:/home/trainee:/bin/bash
vboxadd:x:988:1::/var/run/vboxadd:/bin/false
named:x:25:25:Named:/var/named:/sbin/nologin

trainee@SLES12SP1:~> cat /etc/passwd
at:x:25:25:Batch jobs daemon:/var/spool/atjobs:/bin/bash
bin:x:1:1:bin:/bin:/bin/bash
daemon:x:2:2:Daemon:/sbin:/bin/bash
ftp:x:40:49:FTP account:/srv/ftp:/bin/bash
ftpsecure:x:488:65534:Secure FTP User:/var/lib/empty:/bin/false
games:x:12:100:Games account:/var/games:/bin/bash
gdm:x:486:485:Gnome Display Manager daemon:/var/lib/gdm:/bin/false
lp:x:4:7:Printing daemon:/var/spool/lpd:/bin/bash
mail:x:8:12:Mailer daemon:/var/spool/clientmqueue:/bin/false
man:x:13:62:Manual pages viewer:/var/cache/man:/bin/bash
messagebus:x:499:499:User for D-Bus:/var/run/dbus:/bin/false
news:x:9:13:News system:/etc/news:/bin/bash
nobody:x:65534:65533:nobody:/var/lib/nobody:/bin/bash
nscd:x:496:495:User for nscd:/run/nscd:/sbin/nologin
ntp:x:74:492:NTP daemon:/var/lib/ntp:/bin/false
openslp:x:494:2:openslp daemon:/var/lib/empty:/sbin/nologin
polkitd:x:497:496:User for polkitd:/var/lib/polkit:/sbin/nologin
postfix:x:51:51:Postfix Daemon:/var/spool/postfix:/bin/false
pulse:x:490:489:PulseAudio daemon:/var/lib/pulseaudio:/sbin/nologin
root:x:0:0:root:/root:/bin/bash
rpc:x:495:65534:user for rpcbind:/var/lib/empty:/sbin/nologin
rtkit:x:491:490:RealtimeKit:/proc:/bin/false
scard:x:487:487:Smart Card Reader:/var/run/pcscd:/usr/sbin/nologin
sshd:x:498:498:SSH daemon:/var/lib/sshd:/bin/false
statd:x:489:65534:NFS statd daemon:/var/lib/nfs:/sbin/nologin
usbmux:x:493:65534:usbmuxd daemon:/var/lib/usbmuxd:/sbin/nologin
uucp:x:10:14:Unix-to-Unix CoPy system:/etc/uucp:/bin/bash
vnc:x:492:491:user for VNC:/var/lib/empty:/sbin/nologin
wwwrun:x:30:8:WWW daemon apache:/var/lib/wwwrun:/bin/false
trainee:x:1000:100:trainee:/home/trainee:/bin/bas

However, each user can change his shell using the chsh command. The shells available to users are listed in the /etc/shells file:

trainee@debian8:~$ cat /etc/shells
# /etc/shells: valid login shells
/bin/sh
/bin/dash
/bin/bash
/bin/rbash
/usr/bin/screen

trainee@ubuntu1604:~$ cat /etc/shells
# /etc/shells: valid login shells
/bin/sh
/bin/dash
/bin/bash
/bin/rbash
/usr/bin/screen

[trainee@centos7 ~]$ cat /etc/shells
/bin/sh
/bin/bash
/sbin/nologin
/usr/bin/sh
/usr/bin/bash
/usr/sbin/nologin
/bin/tcsh
/bin/csh

trainee@SLES12SP1:~> cat /etc/shells
/bin/ash
/bin/bash
/bin/csh
/bin/dash
/bin/false
/bin/ksh
/bin/ksh93
/bin/mksh
/bin/pdksh
/bin/sh
/bin/tcsh
/bin/true
/bin/zsh
/usr/bin/csh
/usr/bin/dash
/usr/bin/ksh
/usr/bin/ksh93
/usr/bin/mksh
/usr/bin/passwd
/usr/bin/pdksh
/usr/bin/bash
/usr/bin/tcsh
/usr/bin/zsh

Now use the echo command to view the contents of the system variable SHELL for your current session:

trainee@debian8:~$ echo $SHELL
/bin/bash

trainee@ubuntu1604:~$ echo $SHELL
/bin/bash

[trainee@centos7 ~]$ echo $SHELL
/bin/bash

trainee@SLES12SP1:~> echo $SHELL
/bin/bash

Important : Note that when using RHEL/CentOS 7 the output shows that trainee's shell is /bin/bash and not /usr/bin/bash. This is because /bin is a soft link to /usr/bin.

Now change your shell to /bin/sh using the chsh command:

trainee@debian8:~$ chsh
Password: trainee
Changing the login shell for trainee
Enter the new value, or press ENTER for the default
	Login Shell [/bin/bash]: /bin/sh

trainee@ubuntu1604:~$ chsh
Password: trainee
Changing the login shell for trainee
Enter the new value, or press ENTER for the default
	Login Shell [/bin/bash]: /bin/sh

[trainee@centos7 ~]$ chsh
Changing shell for trainee.
New shell [/bin/bash]: /bin/sh
Password: trainee
Shell changed.

trainee@SLES12SP1:~> chsh
Password: trainee
Changing the login shell for trainee
Enter the new value, or press ENTER for the default
	Login Shell [/bin/bash]: /bin/sh

Important: Note that the password will not be printed to standard output.

Now check your current shell:

trainee@debian8:~$ echo $SHELL
/bin/bash

trainee@ubuntu1604:~$ echo $SHELL
/bin/bash

[trainee@centos7 ~]$ echo $SHELL
/bin/bash

trainee@SLES12SP1:~> echo $SHELL
/bin/bash

At first glance nothing has happened. However if you view your entry in the /etc/passwd file you will notice that your login shell has changed:

trainee@debian8:~$ cat /etc/passwd | grep trainee
trainee:x:1000:1000:trainee,,,:/home/trainee:/bin/sh

trainee@ubuntu1604:~$ cat /etc/passwd | grep trainee
trainee:x:1000:1000:trainee,,,:/home/trainee:/bin/sh

[trainee@centos7 ~]$ cat /etc/passwd | grep trainee
trainee:x:1000:1000:trainee:/home/trainee:/bin/sh

trainee@SLES12SP1:~> cat /etc/passwd | grep trainee
trainee:x:1000:100:trainee:/home/trainee:/bin/sh

Important : The /bin/sh shell will be your active shell the next time you login.

Now change your shell back to /bin/bash using the chsh command:

trainee@debian8:~$ chsh
Password: trainee
Changing the login shell for trainee
Enter the new value, or press ENTER for the default
	Login Shell [/bin/sh]: /bin/bash

trainee@ubuntu1604:~$ chsh
Password: trainee
Changing the login shell for trainee
Enter the new value, or press ENTER for the default
	Login Shell [/bin/sh]: /bin/bash

[trainee@centos7 ~]$ chsh
Changing shell for trainee.
New shell [/bin/sh]: /bin/bash
Password: trainee
Shell changed.

trainee@SLES12SP1:~> chsh
Password: trainee
Changing the login shell for trainee
Enter the new value, or press ENTER for the default
	Login Shell [/bin/sh]: /bin/bash

Important: Note that the password will not be printed to standard output.

The Prompt

As you have already noticed, the prompt under Linux is different for a normal user and root:

$ for a user when using RHEL/CentOS, Debian and Ubuntu,
> for a user when using SLES,
# for root.

The history Command

/bin/bash keeps track of commands that have been previously executed. To access the command history, use the following command:

trainee@debian8:~$ history | more
    1  su -
    2  su -
    3  exit
    4  su -
    5  exit
    6  ls -l /var
    7  su -
    8  su -
    9  vi vitext
   10  view vitext
   11  clear
   12  stty -a
   13  date
   14  who
   15  df
   16  df -h
   17  free
   18  free -h
   19  whoami
   20  su -
   21  clear
   22  su -
   23  exit
--More--

trainee@ubuntu1604:~$ history | more
    1  sudo su -
    2  vi vitext
    3  view vitext
    4  vi vitext
    5  vi .exrc
    6  vi vitext
    7  clear
    8  stty -a
    9  date
   10  locale
   11  LANG=en_GB.UTF-8
   12  export LANG
   13  locale
   14  date
   15  LC_ALL=en_GB.UTF-8
   16  export LC_ALL
   17  locale
   18  date
   19  who
   20  df
   21  df -h
   22  free
   23  free -h
--More--

[trainee@centos7 ~]$ history | more
    1  su -
    2  df -h
    3  su -
    4  exit
    5  su -
    6  su -
    7  vi vitext
    8  view vitext
    9  vi vitext
   10  locale
   11  LANG=en_GB.UTF-8
   12  export LANG
   13  locale
   14  vi vitext
   15  vi .exrc
   16  vi vitext
   17  clear
   18  stty -a
   19  date
   20  locale
   21  who
   22  df
   23  df -h
--More--

trainee@SLES12SP1:~> history | more
    1  su -
    2  su -
    3  clear
    4  cd /
    5  ls -l
    6  ls -l /var/run
    7  cd /mnt
    8  ls
    9  cd 
   10  mount
   11  mount --help
   12  cat /etc/fstab
   13  umount --help
   14  dumpe2fs /dev/sda1 | grep -i superbloc
   15  ls -ld /dev/console /dev/initctl /dev/loop0 /etc /etc/passwd
   16  ls -ld /dev/console /dev/initctl /etc /etc/passwd
   17  ls -ldi /dev/console /dev/initctl /etc /etc/passwd
   18  cd /tmp; mkdir inode; cd inode; touch fichier1; ls -ali
   19  ln fichier1 fichier2
   20  ls -ali
   21  ln -s fichier1 fichier3
   22  ls -ali
   23  su -
--More--

Important: The history is specific to each user.

The history command uses emacs style control characters. As a result you can navigate through the list as follows:

Control Character	Action
[CTRL]-[P] (= Up Arrow)	Navigates backwards through the list
[CTRL]-[N] (= Down Arrow)	Navigates forwards through the list

To move around in the history:

Control Character	Action
[CTRL]-[A]	Move to the beginning of the line
[CTRL]-[E]	Move to the end of the line
[CTRL]-[B]	Move one character to the left
[CTRL]-[F]	Move one character to the right
[CTRL]-[D]	Delete the character under the cursor

Pour rechercher dans l'historique il convient d'utiliser les touches :

Control Character	Action
[CTRL]-[R] string	Search backwards for string in the history. Using [CTRL]-[R] again will search for the previous occurence of string
[CTRL]-[S] string	Search forwards for string in the history. Using [CTRL]-[S] again will search for the next occurence of string
[CTRL]-[G]	Quit the search mode

It is also possible to recall the last command executed by using the !! characters:

trainee@debian8:~$ ls
aac  bca      Documents  Music     Public     Videos  xyz
abc  Desktop  Downloads  Pictures  Templates  vitext
trainee@debian8:~$ !!
ls
aac  bca      Documents  Music     Public     Videos  xyz
abc  Desktop  Downloads  Pictures  Templates  vitext

trainee@ubuntu1604:~$ ls
aac  bca      Documents  examples.desktop  Pictures  Templates  vitext
abc  Desktop  Downloads  Music             Public    Videos     xyz
trainee@ubuntu1604:~$ !!
ls
aac  bca      Documents  examples.desktop  Pictures  Templates  vitext
abc  Desktop  Downloads  Music             Public    Videos     xyz

[trainee@centos7 ~]$ ls
aac  bca      Documents  Music     Public     Videos  xyz
abc  Desktop  Downloads  Pictures  Templates  vitext
[trainee@centos7 ~]$ !!
ls
aac  bca      Documents  Music     Public     Videos  xyz
abc  Desktop  Downloads  Pictures  Templates  vitext

trainee@SLES12SP1:~> ls
aac  bca  Desktop    Downloads  Pictures  public_html  Videos  xyz
abc  bin  Documents  Music      Public    Templates    vitext
trainee@SLES12SP1:~> !!
ls
aac  bca  Desktop    Downloads  Pictures  public_html  Videos  xyz
abc  bin  Documents  Music      Public    Templates    vitext

Alternatively, to execute a command in the list, you can use the list number preceded by the ! character:

trainee@debian8:~$ !52
ls
aac  bca      Documents  Music     Public     Videos  xyz
abc  Desktop  Downloads  Pictures  Templates  vitext

trainee@ubuntu1604:~$ !107
ls
aac  bca      Documents  examples.desktop  Pictures  Templates  vitext
abc  Desktop  Downloads  Music             Public    Videos     xyz

[trainee@centos7 ~]$ !123
ls
aac  bca      Documents  Music     Public     Videos  xyz
abc  Desktop  Downloads  Pictures  Templates  vitext

trainee@SLES12SP1:~> !131
ls
aac  bca  Desktop    Downloads  Pictures  public_html  Videos  xyz
abc  bin  Documents  Music      Public    Templates    vitext

The environmental variables associated with the history are set system-wide in the /etc/profile file. When using Debian or Ubuntu however, the values are set in the ~/.bashrc file where ~/ indicates the home directory of the user concerned:

trainee@debian8:~$ cat .bashrc | grep HISTSIZE
# for setting history length see HISTSIZE and HISTFILESIZE in bash(1)
HISTSIZE=1000

trainee@ubuntu1604:~$ cat .bashrc | grep HISTSIZE
# for setting history length see HISTSIZE and HISTFILESIZE in bash(1)
HISTSIZE=1000

[trainee@centos7 ~]$ cat /etc/profile | grep HISTSIZE
HISTSIZE=1000
export PATH USER LOGNAME MAIL HOSTNAME HISTSIZE HISTCONTROL

trainee@SLES12SP1:~> cat /etc/profile | grep HISTSIZE
    HISTSIZE=1000
    export HISTSIZE

As you can see, in the previous case the HISTSIZE value is set to 1000. This means that the last 1,000 commands are held in the history.

The history command stores data in the ~/.bash_history file for each user. The commands for the current bash session are stored in the file when the session is closed:

trainee@debian8:~$ nl .bash_history | more
     1	su -
     2	su -
     3	exit
     4	su -
     5	exit
     6	ls -l /var
     7	su -
     8	su -
     9	vi vitext
    10	view vitext
    11	clear
    12	stty -a
    13	date
    14	who
    15	df
    16	df -h
    17	free
    18	free -h
    19	whoami
    20	su -
    21	clear
    22	su -
    23	exit
--More--

trainee@ubuntu1604:~$ nl .bash_history | more
     1	sudo su -
     2	vi vitext
     3	view vitext
     4	vi vitext
     5	vi .exrc
     6	vi vitext
     7	clear
     8	stty -a
     9	date
    10	locale
    11	LANG=en_GB.UTF-8
    12	export LANG
    13	locale
    14	date
    15	LC_ALL=en_GB.UTF-8
    16	export LC_ALL
    17	locale
    18	date
    19	who
    20	df
    21	df -h
    22	free
    23	free -h
--More--

[trainee@centos7 ~]$ nl .bash_history | more
     1	su -
     2	df -h
     3	su -
     4	exit
     5	su -
     6	su -
     7	vi vitext
     8	view vitext
     9	vi vitext
    10	locale
    11	LANG=en_GB.UTF-8
    12	export LANG
    13	locale
    14	vi vitext
    15	vi .exrc
    16	vi vitext
    17	clear
    18	stty -a
    19	date
    20	locale
    21	who
    22	df
    23	df -h
--More--

trainee@SLES12SP1:~> nl .bash_history | more
     1	su -
     2	su -
     3	clear
     4	cd /
     5	ls -l
     6	ls -l /var/run
     7	cd /mnt
     8	ls
     9	cd -
    10	mount
    11	mount --help
    12	cat /etc/fstab
    13	umount --help
    14	dumpe2fs /dev/sda1 | grep -i superbloc
    15	ls -ld /dev/console /dev/initctl /dev/loop0 /etc /etc/passwd
    16	ls -ld /dev/console /dev/initctl /etc /etc/passwd
    17	ls -ldi /dev/console /dev/initctl /etc /etc/passwd
    18	cd /tmp; mkdir inode; cd inode; touch fichier1; ls -ali
    19	ln fichier1 fichier2
    20	ls -ali
    21	ln -s fichier1 fichier3
    22	ls -ali
    23	su -
--More--

Important : Note the use of the nl command to number the lines in the output of the contents of .bash_history file.

The TAB key

/bin/bash can auto-generate the end of a file name. Consider the following example:

$ ls .b [Tab][Tab][Tab]

By hitting the Tab key three times, the system shows you the files that match:

trainee@debian8:~$ ls .bash
.bash_history  .bash_logout   .bashrc

trainee@ubuntu1604:~$ ls .bash
.bash_history  .bash_logout   .bashrc

[trainee@centos7 ~]$ ls .bash
.bash_history  .bash_logout   .bash_profile  .bashrc

trainee@SLES12SP1:~> ls .bash
.bash_history  .bashrc

Important : Note that when using Debian or Ubuntu, the .bash_profile file does not exist. In the case of both of these distributions, the file is replaced by the .profile file.

This same technique can also be used to auto-generate command names. Consider the following example:

$ mo [Tab][Tab]

By hitting the Tab twice the system lists all known commands available to the user and starting with mo:

trainee@debian8:~$ mo
moc         moggsplit   more        mount       mountpoint  mousepad

trainee@ubuntu1604:~$ mo
moc               mogrify-im6       mount             mount.ntfs        
modinfo           montage           mountall          mount.ntfs-3g     
modprobe          montage-im6       mount.fuse        mountpoint        
mogrify           more              mount.lowntfs-3g  mousetweaks

[trainee@centos7 ~]$ mo
mobj_dump        modutil          mount.cifs       mount.nfs4       mousetweaks
modifyrepo       mokutil          mount.fuse       mountpoint       
modinfo          more             mount.glusterfs  mountstats       
modprobe         mount            mount.nfs        mount.vboxsf

trainee@SLES12SP1:~> mo
modeprint       modsign-verify  mount           mouse-test      
modetest        more            mountpoint

Metacharacters

It is often necessary and desirable to be able to work with several files at one time as opposed to repeating the operation on each file individually. For this reason, bash accepts the use of Metacharacters:

Metacharacter	Description
*	Matches one or more characters
?	Matches a single character
[abc]	Matches any one of the characters between square brackets
[!abc]	Matches any character except those between square brackets
[m-t]	Matches any character from m through to t
[!m-t]	Matches any character other than m through to t
?(expression1\|expression2\| …)	Matches 0 or 1 occurence of expression1 OR 0 or 1 occurence of expression2 OR …
*(expression1\|expression2\| …)	Matches 0 to x occurences of expression1 OR 0 to x occurences of expression2 OR …
+(expression1\|expression2\| …)	Matches 1 to x occurences of expression1 OR 1 to x occurences of expression2 OR …
@(expression1\|expression2\| …)	Matches 1 occurrence of expression1 OR 1 occurence of expression2 OR …
!(expression1\|expression2\| …)	Matches 0 occurrences of expression1 OR 0 occurrences of expression2 OR …

To illustrate the use of Metacharacters, you need to create a directory in your home directory and the create some files within it:

trainee@debian8:~$ mkdir training
trainee@debian8:~$ cd training
trainee@debian8:~/training$ touch f1 f2 f3 f4 f5

trainee@ubuntu1604:~$ mkdir training
trainee@ubuntu1604:~$ cd training
trainee@ubuntu1604:~/training$ touch f1 f2 f3 f4 f5

[trainee@centos7 ~]$ mkdir training
[trainee@centos7 ~]$ cd training
[trainee@centos7 training]$ touch f1 f2 f3 f4 f5

trainee@SLES12SP1:~> mkdir training
trainee@SLES12SP1:~> cd training
trainee@SLES12SP1:~/training> touch f1 f2 f3 f4 f5

The * Metacharacter

Now use the Metacharacter *:

trainee@debian8:~/training$ echo f*
f1 f2 f3 f4 f5

trainee@ubuntu1604:~/training$ echo f*
f1 f2 f3 f4 f5

[trainee@centos7 training]$ echo f*
f1 f2 f3 f4 f5

trainee@SLES12SP1:~/training> echo f*
f1 f2 f3 f4 f5

Important: Note that the * is used as a wild card which replaces 0 or more characters.

The ? Metacharacter

Create two more files:

trainee@debian8:~/training$ touch f52 f62

trainee@ubuntu1604:~/training$ touch f52 f62

[trainee@centos7 training]$ touch f52 f62

trainee@SLES12SP1:~/training> touch f52 f62

Now use the Metacharacter ?:

trainee@debian8:~/training$ echo f?2
f52 f62

trainee@ubuntu1604:~/training$ echo f?2
f52 f62

[trainee@centos7 training]$ echo f?2
f52 f62

trainee@SLES12SP1:~/training> echo f?2
f52 f62

Important: Note that the ? is used as a wild card which replaces a single character.

The [] Metacharacter

The [] Metacharacter can take several forms:

Metacharacter	Description
[xyz]	Represents either x or y or z
[m-t]
[!xyz]	Represents any character other than x or y or z
[!m-t]	Represents any character outside of the range m to t

To demonstrate the use of the metacharacter [], create a file called a100:

trainee@debian8:~/training$ touch a100

trainee@ubuntu1604:~/training$ touch a100

[trainee@centos7 training]$ touch a100

trainee@SLES12SP1:~/training> touch a100

The use of this Metacharacter can be demonstrated with the following examples:

trainee@debian8:~/training$ echo [a-f]*
a100 f1 f2 f3 f4 f5 f52 f62
trainee@debian8:~/training$ echo [af]*
a100 f1 f2 f3 f4 f5 f52 f62

trainee@ubuntu1604:~/training$ echo [a-f]*
a100 f1 f2 f3 f4 f5 f52 f62
trainee@ubuntu1604:~/training$ echo [af]*
a100 f1 f2 f3 f4 f5 f52 f62

[trainee@centos7 training]$ echo [a-f]*
a100 f1 f2 f3 f4 f5 f52 f62
[trainee@centos7 training]$ echo [af]*
a100 f1 f2 f3 f4 f5 f52 f62

trainee@SLES12SP1:~/training> echo [a-f]*
a100 f1 f2 f3 f4 f5 f52 f62
trainee@SLES12SP1:~/training> echo [af]*
a100 f1 f2 f3 f4 f5 f52 f62

Important: Note that all the files starting with either a, b, c, d, e or f are displayed.

trainee@debian8:~/training$ echo [!a]*
f1 f2 f3 f4 f5 f52 f62

trainee@ubuntu1604:~/training$ echo [!a]*
f1 f2 f3 f4 f5 f52 f62

[trainee@centos7 training]$ echo [!a]*
f1 f2 f3 f4 f5 f52 f62

trainee@SLES12SP1:~/training> echo [!a]*
f1 f2 f3 f4 f5 f52 f62

Important: Note that all the files in the directory are displayed except the file starting with a .

trainee@debian8:~/training$ echo [a-b]*
a100

trainee@ubuntu1604:~/training$ echo [a-b]*
a100

[trainee@centos7 training]$ echo [a-b]*
a100

trainee@SLES12SP1:~/training> echo [a-b]*
a100

Important: Note that only the file starting with a is displayed since no file starting with b is present.

trainee@debian8:~/training$ echo [a-f]
[a-f]

trainee@ubuntu1604:~/training$ echo [a-f]
[a-f]

[trainee@centos7 training]$ echo [a-f]
[a-f]

trainee@SLES12SP1:~/training> echo [a-f]
[a-f]

Important: Note that in the above example, since no file called a, b, c, d, e or f exists in the directory, the echo command simply returns the filter used.

The extglob Option

In order to use ?(expression), *(expression), +(expression), @(expression) and !(expression), you need to activate the extglob option:

trainee@debian8:~/training$ shopt -s extglob

trainee@ubuntu1604:~/training$ shopt -s extglob

[trainee@centos7 training]$ shopt -s extglob

trainee@SLES12SP1:~/training> shopt -s extglob

The shopt command is used to activate and deactivate the shopt option of the shell.

The list of all the options can be displayed by simply using the shopt command:

trainee@debian8:~/training$ shopt
autocd         	off
cdable_vars    	off
cdspell        	off
checkhash      	off
checkjobs      	off
checkwinsize   	on
cmdhist        	on
compat31       	off
compat32       	off
compat40       	off
compat41       	off
compat42       	off
complete_fullquote	on
direxpand      	off
dirspell       	off
dotglob        	off
execfail       	off
expand_aliases 	on
extdebug       	off
extglob        	on
extquote       	on
failglob       	off
force_fignore  	on
globstar       	off
globasciiranges	off
gnu_errfmt     	off
histappend     	on
histreedit     	off
histverify     	off
hostcomplete   	off
huponexit      	off
interactive_comments	on
lastpipe       	off
lithist        	off
login_shell    	on
mailwarn       	off
no_empty_cmd_completion	off
nocaseglob     	off
nocasematch    	off
nullglob       	off
progcomp       	on
promptvars     	on
restricted_shell	off
shift_verbose  	off
sourcepath     	on
xpg_echo       	off

trainee@ubuntu1604:~/training$ shopt
autocd         	off
cdable_vars    	off
cdspell        	off
checkhash      	off
checkjobs      	off
checkwinsize   	on
cmdhist        	on
compat31       	off
compat32       	off
compat40       	off
compat41       	off
compat42       	off
complete_fullquote	on
direxpand      	off
dirspell       	off
dotglob        	off
execfail       	off
expand_aliases 	on
extdebug       	off
extglob        	on
extquote       	on
failglob       	off
force_fignore  	on
globstar       	off
globasciiranges	off
gnu_errfmt     	off
histappend     	on
histreedit     	off
histverify     	off
hostcomplete   	off
huponexit      	off
interactive_comments	on
lastpipe       	off
lithist        	off
login_shell    	on
mailwarn       	off
no_empty_cmd_completion	off
nocaseglob     	off
nocasematch    	off
nullglob       	off
progcomp       	on
promptvars     	on
restricted_shell	off
shift_verbose  	off
sourcepath     	on
xpg_echo       	off

[trainee@centos7 training]$ shopt
autocd         	off
cdable_vars    	off
cdspell        	off
checkhash      	off
checkjobs      	off
checkwinsize   	on
cmdhist        	on
compat31       	off
compat32       	off
compat40       	off
compat41       	off
direxpand      	off
dirspell       	off
dotglob        	off
execfail       	off
expand_aliases 	on
extdebug       	off
extglob        	on
extquote       	on
failglob       	off
force_fignore  	on
globstar       	off
gnu_errfmt     	off
histappend     	on
histreedit     	off
histverify     	off
hostcomplete   	off
huponexit      	off
interactive_comments	on
lastpipe       	off
lithist        	off
login_shell    	on
mailwarn       	off
no_empty_cmd_completion	off
nocaseglob     	off
nocasematch    	off
nullglob       	off
progcomp       	on
promptvars     	on
restricted_shell	off
shift_verbose  	off
sourcepath     	on
xpg_echo       	of

trainee@SLES12SP1:~/training> shopt
autocd         	off
cdable_vars    	off
cdspell        	off
checkhash      	off
checkjobs      	off
checkwinsize   	on
cmdhist        	on
compat31       	off
compat32       	off
compat40       	off
compat41       	off
direxpand      	off
dirspell       	off
dotglob        	off
execfail       	off
expand_aliases 	on
extdebug       	off
extglob        	on
extquote       	on
failglob       	off
force_fignore  	on
globstar       	off
gnu_errfmt     	off
histappend     	on
histreedit     	off
histverify     	off
hostcomplete   	off
huponexit      	off
interactive_comments	on
lastpipe       	off
lithist        	off
login_shell    	on
mailwarn       	off
no_empty_cmd_completion	off
nocaseglob     	off
nocasematch    	off
nullglob       	off
progcomp       	on
promptvars     	on
restricted_shell	off
shift_verbose  	off
sourcepath     	on
xpg_echo       	off

?(expression)

Create the following files:

trainee@debian8:~/training$ touch f f.txt f123.txt f123123.txt f123123123.txt

trainee@ubuntu1604:~/training$ touch f f.txt f123.txt f123123.txt f123123123.txt

[trainee@centos7 training]$ touch f f.txt f123.txt f123123.txt f123123123.txt

trainee@SLES12SP1:~/training> touch f f.txt f123.txt f123123.txt f123123123.txt

Execute the following command:

trainee@debian8:~/training$ ls f?(123).txt
f123.txt  f.txt

trainee@ubuntu1604:~/training$ ls f?(123).txt
f123.txt  f.txt

[trainee@centos7 training]$ ls f?(123).txt
f123.txt  f.txt

trainee@SLES12SP1:~/training> ls f?(123).txt
f123.txt  f.txt

Important: Note that the command displays file names that match 0 or 1 occurrences of the string 123.

*(expression)

Execute the following command:

trainee@debian8:~/training$ ls f*(123).txt
f123123123.txt  f123123.txt  f123.txt  f.txt

trainee@ubuntu1604:~/training$ ls f*(123).txt
f123123123.txt  f123123.txt  f123.txt  f.txt

[trainee@centos7 training]$ ls f*(123).txt
f123123123.txt  f123123.txt  f123.txt  f.txt

trainee@SLES12SP1:~/training> ls f*(123).txt
f123123123.txt  f123123.txt  f123.txt  f.txt

Important: Note that the command displays file names that match 0 to x occurrences of the string 123.

+(expression)

Execute the following command:

trainee@debian8:~/training$ ls f+(123).txt
f123123123.txt  f123123.txt  f123.txt

trainee@ubuntu1604:~/training$ ls f+(123).txt
f123123123.txt  f123123.txt  f123.txt

[trainee@centos7 training]$ ls f+(123).txt
f123123123.txt  f123123.txt  f123.txt

trainee@SLES12SP1:~/training> ls f+(123).txt
f123123123.txt  f123123.txt  f123.txt

Important: Note that the command displays file names that match 1 to x occurrences of the string 123..

@(expression)

Execute the following command:

trainee@debian8:~/training$ ls f@(123).txt
f123.txt

trainee@ubuntu1604:~/training$ ls f@(123).txt
f123.txt

[trainee@centos7 training]$ ls f@(123).txt
f123.txt

trainee@SLES12SP1:~/training> ls f@(123).txt
f123.txt

Important: Note that the command displays file names that match 1 occurrence of the string 123.

!(expression)

Execute the following command:

trainee@debian8:~/training$ ls f!(123).txt
f123123123.txt  f123123.txt  f.txt

trainee@ubuntu1604:~/training$ ls f!(123).txt
f123123123.txt  f123123.txt  f.txt

[trainee@centos7 training]$ ls f!(123).txt
f123123123.txt  f123123.txt  f.txt

trainee@SLES12SP1:~/training> ls f!(123).txt
f123123123.txt  f123123.txt  f.txt

Important: Note that the command displays file names that match 0 or x occurrences of the string 123, where x>1.

Protecting Metacharacters

To cancel the wild card effect of a special character, the character needs to be escaped or “protected”:

Character	Description
\	Escapes the character which immediately follows
' '	Protects any character between the two '
“ ”	Protects any character between the two “ except the following: $, \ and '

For example:

trainee@debian8:~/training$ echo * est un caractère spécial
a100 f f1 f123123123.txt f123123.txt f123.txt f2 f3 f4 f5 f52 f62 f.txt est un caractère spécial

trainee@debian8:~/training$ echo \* est un caractère spécial
* est un caractère spécial

trainee@debian8:~/training$ echo "* est un caractère spécial"
* est un caractère spécial

trainee@debian8:~/training$ echo '* est un caractère spécial'
* est un caractère spécial

trainee@ubuntu1604:~/training$ echo * est un caractère spécial
a100 f f1 f123123123.txt f123123.txt f123.txt f2 f3 f4 f5 f52 f62 f.txt est un caractère spécial

trainee@ubuntu1604:~/training$ echo \* est un caractère spécial
* est un caractère spécial

trainee@ubuntu1604:~/training$ echo "* est un caractère spécial"
* est un caractère spécial

trainee@ubuntu1604:~/training$ echo '* est un caractère spécial'
* est un caractère spécial

[trainee@centos7 training]$ echo * est un caractère spécial
a100 f f1 f123123123.txt f123123.txt f123.txt f2 f3 f4 f5 f52 f62 f.txt est un caractère spécial

[trainee@centos7 training]$ echo \* est un caractère spécial
* est un caractère spécial

[trainee@centos7 training]$ echo "* est un caractère spécial"
* est un caractère spécial

[trainee@centos7 training]$ echo '* est un caractère spécial'
* est un caractère spécial

trainee@SLES12SP1:~/training> echo * est un caractère spécial
a100 f f1 f123123123.txt f123123.txt f123.txt f2 f3 f4 f5 f52 f62 f.txt est un caractère spécial

trainee@SLES12SP1:~/training> echo \* est un caractère spécial
* est un caractère spécial

trainee@SLES12SP1:~/training> echo "* est un caractère spécial"
* est un caractère spécial

trainee@SLES12SP1:~/training> echo '* est un caractère spécial'
* est un caractère spécial

Exit Status

Each command returns an exit status when it is executed. This exit status is stored in a special variable: $?.

For example:

trainee@debian8:~/training$ cd ..
trainee@debian8:~$ mkdir codes
trainee@debian8:~$ echo $?
0
trainee@debian8:~$ touch codes/exit.txt
trainee@debian8:~$ rmdir codes
rmdir: failed to remove ‘codes’: Directory not empty
trainee@debian8:~$ echo $?
1

trainee@ubuntu1604:~/training$ cd ..
trainee@ubuntu1604:~$ mkdir codes
trainee@ubuntu1604:~$ echo $?
0
trainee@ubuntu1604:~$ touch codes/exit.txt
trainee@ubuntu1604:~$ rmdir codes
rmdir: failed to remove 'codes': Directory not empty
trainee@ubuntu1604:~$ echo $?
1

[trainee@centos7 training]$ cd ..
[trainee@centos7 ~]$ mkdir codes
[trainee@centos7 ~]$ echo $?
0
[trainee@centos7 ~]$ touch codes/exit.txt
[trainee@centos7 ~]$ rmdir codes
rmdir: failed to remove ‘codes’: Directory not empty
[trainee@centos7 ~]$ echo $?
1

trainee@SLES12SP1:~/training> cd ..
trainee@SLES12SP1:~> mkdir codes
trainee@SLES12SP1:~> echo $?
0
trainee@SLES12SP1:~> touch codes/exit.txt
trainee@SLES12SP1:~> rmdir codes
rmdir: failed to remove ‘codes’: Directory not empty
trainee@SLES12SP1:~> echo $?
1

As you can see when the exit status is 0, the command executes correctly. If the exit status is anything else, the command executes with errors.

Redirections

Your dialogue with the system uses three file descriptors:

Standard Input - the keyboard,
Standard output - the screen,
Standard error - contains any eventual errors.

The standard output can be redirected using the > character:

trainee@debian8:~$ pwd
/home/trainee
trainee@debian8:~$ cd training
trainee@debian8:~/training$ free > file
trainee@debian8:~/training$ cat file
             total       used       free     shared    buffers     cached
Mem:        506268     429624      76644       4804      59540     130524
-/+ buffers/cache:     239560     266708
Swap:      2046972          0    2046972

trainee@ubuntu1604:~$ pwd
/home/trainee
trainee@ubuntu1604:~$ cd training
trainee@ubuntu1604:~/training$ free > file
trainee@ubuntu1604:~/training$ cat file
              total        used        free      shared  buff/cache   available
Mem:         500144      160208        6548        5168      333388      307548
Swap:       1997820           0     1997820

[trainee@centos7 ~]$ pwd
/home/trainee
[trainee@centos7 ~]$ cd training
[trainee@centos7 training]$ free > file
[trainee@centos7 training]$ cat file
              total        used        free      shared  buff/cache   available
Mem:         500780      192692       38916        4824      269172      260472
Swap:       2096124           0     2096124

trainee@SLES12SP1:~> pwd
/home/trainee
trainee@SLES12SP1:~> cd training
trainee@SLES12SP1:~/training> free > file
trainee@SLES12SP1:~/training> cat file
             total       used       free     shared    buffers     cached
Mem:        394524     386024       8500       5716        452     300420
-/+ buffers/cache:      85152     309372
Swap:      2103292          4    2103288

Important: If the file does not exist, it is automatically created.

Repeating a single redirection will replace the file:

trainee@debian8:~/training$ date > file
trainee@debian8:~/training$ cat file
Mon 28 Nov 14:48:03 GMT 2016

trainee@ubuntu1604:~/training$ date > file
trainee@ubuntu1604:~/training$ cat file
Mon 28 Nov 15:51:07 CET 2016

[trainee@centos7 training]$ date > file
[trainee@centos7 training]$ cat file
Mon 28 Nov 15:48:09 CET 2016

trainee@SLES12SP1:~/training> date > file
trainee@SLES12SP1:~/training> cat file
Mon 28 Nov 15:48:29 CET 2016

To add additional data to the file, you need to use a double redirection:

trainee@debian8:~/training$ free >> file
trainee@debian8:~/training$ cat file
Mon 28 Nov 14:48:03 GMT 2016
             total       used       free     shared    buffers     cached
Mem:        506268     431668      74600       4804      60264     130912
-/+ buffers/cache:     240492     265776
Swap:      2046972          0    20469722

trainee@ubuntu1604:~/training$ free >> file
trainee@ubuntu1604:~/training$ cat file
Mon 28 Nov 15:51:07 CET 2016
              total        used        free      shared  buff/cache   available
Mem:         500144      160208        6436        5168      333500      307548
Swap:       1997820           0     1997820

[trainee@centos7 training]$ free >> file
[trainee@centos7 training]$ cat file
Mon 28 Nov 15:48:09 CET 2016
              total        used        free      shared  buff/cache   available
Mem:         500780      192792       38516        4824      269472      260376
Swap:       2096124           0     2096124

trainee@SLES12SP1:~/training> free >> file
trainee@SLES12SP1:~/training> cat file
Mon 28 Nov 15:48:29 CET 2016
             total       used       free     shared    buffers     cached
Mem:        394524     386876       7648       5716        452     300936
-/+ buffers/cache:      85488     309036
Swap:      2103292          4    2103288

Important : Note that standard output can only be redirected to a single destination.

File descriptors are numbered for ease of use :

0 = Standard Input
1 = Standard Output
2 = Standard Error

For example:

trainee@debian8:~/training$ cd ..
trainee@debian8:~$ rmdir training/ 2>errorlog
trainee@debian8:~$ cat erreurlog
rmdir: failed to remove ‘training/’: Directory not empty

trainee@ubuntu1604:~/training$ cd ..
trainee@ubuntu1604:~$ rmdir training/ 2>errorlog
trainee@ubuntu1604:~$ cat erreurlog
rmdir: failed to remove 'training/': Directory not empty

[trainee@centos7 training]$ cd ..
[trainee@centos7 ~]$ rmdir training/ 2>errorlog
[trainee@centos7 ~]$ cat erreurlog
rmdir: failed to remove ‘training/’: Directory not emptyy

trainee@SLES12SP1:~/training> cd ..
trainee@SLES12SP1:~> rmdir training/ 2>errorlog
trainee@SLES12SP1:~> cat erreurlog
rmdir: failed to remove ‘training/’: Directory not empty

Important: As you can see the error generated is redirected to the errorlog file.

You can join file descriptors using the & character:

trainee@debian8:~$ free > file 2>&1

trainee@ubuntu1604:~$ free > file 2>&1

[trainee@centos7 ~]$ free > file 2>&1

trainee@SLES12SP1:~> free > file 2>&1

Any errors are sent to the same destination as the standard output, in the case, file.

It is also possible to have a reverse redirection:

trainee@debian8:~$ wc -w < errorlog
8

trainee@ubuntu1604:~$ wc -w < errorlog
8

[trainee@centos7 ~]$ wc -w < errorlog
8

trainee@SLES12SP1:~> wc -w < errorlog
8

In this case wc -w counts the number of words in the file.

Other redirections exist :

Redirection	Definition
&>	Join file descriptors 1 and 2.
<<	Takes the text typed on the next lines as standard input until EOF is found at the beginning of a line.
<>	Allows the use of the same file as STDIN and STDOUT.

Pipes

A pipe is used to present the standard output on the first command to the standard input of the second command:

trainee@debian8:~$ ls | wc -w
17

trainee@ubuntu1604:~$ ls | wc -w
17

[trainee@centos7 ~]$ ls | wc -w
17

trainee@SLES12SP1:~> ls | wc -w
18

Important - Several pipes can be used within the same command.

Standard output can generally only be redirected to a single destination. To redirect to two destinations at once, you need to use the tee command:

trainee@debian8:~$ date | tee file1
Mon 28 Nov 15:14:18 GMT 2016
trainee@debian8:~$ cat file1
Mon 28 Nov 15:14:18 GMT 2016

trainee@ubuntu1604:~$ date | tee file1
Mon 28 Nov 16:14:22 CET 2016
trainee@ubuntu1604:~$ cat file1
Mon 28 Nov 16:14:22 CET 2016

[trainee@centos7 ~]$ date | tee file1
Mon 28 Nov 16:14:24 CET 2016
[trainee@centos7 ~]$ cat file1
Mon 28 Nov 16:14:24 CET 2016

trainee@SLES12SP1:~> date | tee file1
Mon 28 Nov 16:14:43 CET 2016
trainee@SLES12SP1:~> cat file1
Mon 28 Nov 16:14:43 CET 2016

Alternatively, tee can be used to redirect to two files at the same time:

trainee@debian8:~$ date | tee fichier1 > fichier2
trainee@debian8:~$ cat fichier1
Mon 28 Nov 15:15:52 GMT 2016
trainee@debian8:~$ cat fichier2
Mon 28 Nov 15:15:52 GMT 2016

trainee@ubuntu1604:~$ date | tee fichier1 > fichier2
trainee@ubuntu1604:~$ cat fichier1
Mon 28 Nov 16:15:56 CET 2016
trainee@ubuntu1604:~$ cat fichier2
Mon 28 Nov 16:15:56 CET 2016

[trainee@centos7 ~]$ date | tee fichier1 > fichier2
[trainee@centos7 ~]$ cat fichier1
Mon 28 Nov 16:15:57 CET 2016
[trainee@centos7 ~]$ cat fichier2
Mon 28 Nov 16:15:57 CET 2016

trainee@SLES12SP1:~> date | tee fichier1 > fichier2
trainee@SLES12SP1:~> cat fichier1
Mon 28 Nov 16:16:15 CET 2016
trainee@SLES12SP1:~> cat fichier2
Mon 28 Nov 16:16:15 CET 2016

Important : The default action of the tee command is to overwrite the destination file. In order to append output to the same file, you need to use the -a switch.

Command Substitution

Command substitution permits in-line execution of a command:

trainee@debian8:~$ echo date
date
trainee@debian8:~$ echo $(date)
Mon 28 Nov 15:19:29 GMT 2016
trainee@debian8:~$ echo `date`
Mon 28 Nov 15:19:30 GMT 2016

trainee@ubuntu1604:~$ echo date
date
trainee@ubuntu1604:~$ echo $(date)
Mon 28 Nov 16:19:33 CET 2016
trainee@ubuntu1604:~$ echo `date`
Mon 28 Nov 16:19:33 CET 2016

[trainee@centos7 ~]$ echo date
date
[trainee@centos7 ~]$ echo $(date)
Mon 28 Nov 16:19:35 CET 2016
[trainee@centos7 ~]$ echo `date`
Mon 28 Nov 16:19:35 CET 2016

trainee@SLES12SP1:~> echo date
date
trainee@SLES12SP1:~> echo $(date)
Mon 28 Nov 16:19:53 CET 2016
trainee@SLES12SP1:~> echo `date`
Mon 28 Nov 16:19:53 CET 2016

Conditional Command Execution

Commands can be grouped using brackets:

$ (ls -l; ps; who) > list

Conditional command execution can be obtained by using the exit status value and either && or ||.

For example,

Command1 && Command2,
- Command2 will execute if the exit status of Command1 is 0,
Command1 || Command2,
- Command2 will execute if the exit status of Command1 anything other than 0.

Environment Variables

The contents of a shell variable can be displayed on standard output using the echo command:

$ echo $VARIABLE [Enter]

Principal Variables

Variable	Description
BASH	Complete path to current shell.
BASH_VERSION	Shell version.
EUID	EUID of the current user.
UID	UID of the current user.
PPID	PID of the parent of the current process.
PWD	The current directory.
OLDPWD	The previous current directory ( like the cd -command ).
RANDOM	A random number between 0 and 32767.
SECONDS	The numbers of seconds since the shell was started.
LINES	The number of lines in a screen.
COLUMNS	The number of columns in a screen .
HISTFILE	The history file.
HISTFILESIZE	The history file size.
HISTSIZE	The number of commands that can be saved to the history file.
HISTCMD	The current command's number in the History.
HISTCONTROL	ignorespace or ignoredups or ignoreboth
HOME	The user's home directory.
HOSTTYPE	Machine type.
OSTYPE	The OS type.
MAIL	The file containing the user's mail.
MAILCHECK	Frequency in seconds that a user's mail is checked.
PATH	The paths to executables.
PROMPT_COMMAND	Command executed before each prompt is displayed.
PS1	User's default prompt.
PS2	User's 2nd level default prompt.
PS3	User's 3rd level prompt.
PS4	User's 4th level prompt.
SHELL	User's current shell.
SHLVL	The number of shell instances.
TMOUT	The number of seconds less 60 before an unused terminal gets sent the exit command.

Internationalisation and Localisation

Internationalisation, also called i18n since there are 18 letters between the I and n, consists of modifying software so that it conforms to regional parameters:

Text processing differences,
Writing direction,
Different systems of numerals,
Telephone numbers, addresses and international postal codes,
Weights and measures,
Date/time format,
Paper sizes,
Keyboard layout,
etc …

Localisation, also called L10n since there are 10 letters between the L and n, consists of modifying the Internationalisation so that it conforms to a specific locale:

en_GB = Great Britain,
en_US = USA,
en_AU = Australia,
en_NZ = New Zealand,
en_ZA = South Africa,
en_CA = Canada.

The most important variables are:

trainee@debian8:~$ echo $LC_ALL
en_GB.UTF-8
trainee@debian8:~$ echo $LC_CTYPE

trainee@debian8:~$ echo $LANG
en_GB.UTF-8

trainee@debian8:~$ locale
LANG=en_GB.UTF-8
LANGUAGE=en_GB:en
LC_CTYPE="en_GB.UTF-8"
LC_NUMERIC="en_GB.UTF-8"
LC_TIME="en_GB.UTF-8"
LC_COLLATE="en_GB.UTF-8"
LC_MONETARY="en_GB.UTF-8"
LC_MESSAGES="en_GB.UTF-8"
LC_PAPER="en_GB.UTF-8"
LC_NAME="en_GB.UTF-8"
LC_ADDRESS="en_GB.UTF-8"
LC_TELEPHONE="en_GB.UTF-8"
LC_MEASUREMENT="en_GB.UTF-8"
LC_IDENTIFICATION="en_GB.UTF-8"
LC_ALL=en_GB.UTF-8

trainee@ubuntu1604:~$ echo $LC_ALL
en_GB.UTF-8
trainee@ubuntu1604:~$ echo $LC_CTYPE

trainee@ubuntu1604:~$ echo $LANG
en_GB.UTF-8

trainee@ubuntu1604:~$ locale
LANG=en_GB.UTF-8
LANGUAGE=
LC_CTYPE="en_GB.UTF-8"
LC_NUMERIC="en_GB.UTF-8"
LC_TIME="en_GB.UTF-8"
LC_COLLATE="en_GB.UTF-8"
LC_MONETARY="en_GB.UTF-8"
LC_MESSAGES="en_GB.UTF-8"
LC_PAPER="en_GB.UTF-8"
LC_NAME="en_GB.UTF-8"
LC_ADDRESS="en_GB.UTF-8"
LC_TELEPHONE="en_GB.UTF-8"
LC_MEASUREMENT="en_GB.UTF-8"
LC_IDENTIFICATION="en_GB.UTF-8"
LC_ALL=en_GB.UTF-8

[trainee@centos7 ~]$ echo $LC_ALL
en_GB.UTF-8
[trainee@centos7 ~]$ echo $LC_CTYPE

[trainee@centos7 ~]$ echo $LANG
en_GB.UTF-8 

[trainee@centos7 ~]$ locale
LANG=en_GB.UTF-8
LC_CTYPE="en_GB.UTF-8"
LC_NUMERIC="en_GB.UTF-8"
LC_TIME="en_GB.UTF-8"
LC_COLLATE="en_GB.UTF-8"
LC_MONETARY="en_GB.UTF-8"
LC_MESSAGES="en_GB.UTF-8"
LC_PAPER="en_GB.UTF-8"
LC_NAME="en_GB.UTF-8"
LC_ADDRESS="en_GB.UTF-8"
LC_TELEPHONE="en_GB.UTF-8"
LC_MEASUREMENT="en_GB.UTF-8"
LC_IDENTIFICATION="en_GB.UTF-8"
LC_ALL=en_GB.UTF-8

trainee@SLES12SP1:~> echo $LC_ALL
en_GB.UTF-8
trainee@SLES12SP1:~> echo $LC_CTYPE

trainee@SLES12SP1:~> echo $LANG
en_GB.UTF-8

trainee@SLES12SP1:~> locale
LANG=en_GB.UTF-8
LC_CTYPE="en_GB.UTF-8"
LC_NUMERIC="en_GB.UTF-8"
LC_TIME="en_GB.UTF-8"
LC_COLLATE="en_GB.UTF-8"
LC_MONETARY="en_GB.UTF-8"
LC_MESSAGES="en_GB.UTF-8"
LC_PAPER="en_GB.UTF-8"
LC_NAME="en_GB.UTF-8"
LC_ADDRESS="en_GB.UTF-8"
LC_TELEPHONE="en_GB.UTF-8"
LC_MEASUREMENT="en_GB.UTF-8"
LC_IDENTIFICATION="en_GB.UTF-8"
LC_ALL=en_GB.UTF-8

Special Variables

Variable	Description
$LINENO	Contains the current line number of the script or function being executed
$$	Contains the PID of the current process
$PPID	Contains the PID of the parent of the current process
$0	Contains the name of the current script
$1, $2 …	Contains respectively the 1st, 2nd etc arguments passed to the script
$#	Contains the total number of arguments passed to the script
$*	Contains all of the arguments passed to the script
$@	Contains all of the arguments passed to the script

The env Commande

The env command can be used to run a program in a modified environment or just list the values of all environmental variables associated with the user calling the program env:

trainee@debian8:~$ env
XDG_SESSION_ID=1
TERM=xterm-256color
SHELL=/bin/bash
SSH_CLIENT=10.0.2.2 44524 22
OLDPWD=/home/trainee/training
SSH_TTY=/dev/pts/0
LC_ALL=en_GB.UTF-8
USER=trainee
LS_COLORS=rs=0:di=01;34:ln=01;36:mh=00:pi=40;33:so=01;35:do=01;35:bd=40;33;01:cd=40;33;01:or=40;31;01:su=37;41:sg=30;43:ca=30;41:tw=30;42:ow=34;42:st=37;44:ex=01;32:*.tar=01;31:*.tgz=01;31:*.arc=01;31:*.arj=01;31:*.taz=01;31:*.lha=01;31:*.lz4=01;31:*.lzh=01;31:*.lzma=01;31:*.tlz=01;31:*.txz=01;31:*.tzo=01;31:*.t7z=01;31:*.zip=01;31:*.z=01;31:*.Z=01;31:*.dz=01;31:*.gz=01;31:*.lrz=01;31:*.lz=01;31:*.lzo=01;31:*.xz=01;31:*.bz2=01;31:*.bz=01;31:*.tbz=01;31:*.tbz2=01;31:*.tz=01;31:*.deb=01;31:*.rpm=01;31:*.jar=01;31:*.war=01;31:*.ear=01;31:*.sar=01;31:*.rar=01;31:*.alz=01;31:*.ace=01;31:*.zoo=01;31:*.cpio=01;31:*.7z=01;31:*.rz=01;31:*.cab=01;31:*.jpg=01;35:*.jpeg=01;35:*.gif=01;35:*.bmp=01;35:*.pbm=01;35:*.pgm=01;35:*.ppm=01;35:*.tga=01;35:*.xbm=01;35:*.xpm=01;35:*.tif=01;35:*.tiff=01;35:*.png=01;35:*.svg=01;35:*.svgz=01;35:*.mng=01;35:*.pcx=01;35:*.mov=01;35:*.mpg=01;35:*.mpeg=01;35:*.m2v=01;35:*.mkv=01;35:*.webm=01;35:*.ogm=01;35:*.mp4=01;35:*.m4v=01;35:*.mp4v=01;35:*.vob=01;35:*.qt=01;35:*.nuv=01;35:*.wmv=01;35:*.asf=01;35:*.rm=01;35:*.rmvb=01;35:*.flc=01;35:*.avi=01;35:*.fli=01;35:*.flv=01;35:*.gl=01;35:*.dl=01;35:*.xcf=01;35:*.xwd=01;35:*.yuv=01;35:*.cgm=01;35:*.emf=01;35:*.axv=01;35:*.anx=01;35:*.ogv=01;35:*.ogx=01;35:*.aac=00;36:*.au=00;36:*.flac=00;36:*.m4a=00;36:*.mid=00;36:*.midi=00;36:*.mka=00;36:*.mp3=00;36:*.mpc=00;36:*.ogg=00;36:*.ra=00;36:*.wav=00;36:*.axa=00;36:*.oga=00;36:*.spx=00;36:*.xspf=00;36:
MAIL=/var/mail/trainee
PATH=/usr/local/bin:/usr/bin:/bin:/usr/local/games:/usr/games
PWD=/home/trainee
LANG=en_GB.UTF-8
SHLVL=1
HOME=/home/trainee
LANGUAGE=en_GB:en
LOGNAME=trainee
SSH_CONNECTION=10.0.2.2 44524 10.0.2.15 22
XDG_RUNTIME_DIR=/run/user/1000
_=/usr/bin/env

trainee@ubuntu1604:~$ env
LC_PAPER=fr_FR.UTF-8
LC_ADDRESS=fr_FR.UTF-8
XDG_SESSION_ID=1
LC_MONETARY=fr_FR.UTF-8
TERM=xterm-256color
SHELL=/bin/bash
SSH_CLIENT=10.0.2.2 40266 22
LC_NUMERIC=fr_FR.UTF-8
OLDPWD=/home/trainee/training
SSH_TTY=/dev/pts/8
LC_ALL=en_GB.UTF-8
USER=trainee
LS_COLORS=rs=0:di=01;34:ln=01;36:mh=00:pi=40;33:so=01;35:do=01;35:bd=40;33;01:cd=40;33;01:or=40;31;01:mi=00:su=37;41:sg=30;43:ca=30;41:tw=30;42:ow=34;42:st=37;44:ex=01;32:*.tar=01;31:*.tgz=01;31:*.arc=01;31:*.arj=01;31:*.taz=01;31:*.lha=01;31:*.lz4=01;31:*.lzh=01;31:*.lzma=01;31:*.tlz=01;31:*.txz=01;31:*.tzo=01;31:*.t7z=01;31:*.zip=01;31:*.z=01;31:*.Z=01;31:*.dz=01;31:*.gz=01;31:*.lrz=01;31:*.lz=01;31:*.lzo=01;31:*.xz=01;31:*.bz2=01;31:*.bz=01;31:*.tbz=01;31:*.tbz2=01;31:*.tz=01;31:*.deb=01;31:*.rpm=01;31:*.jar=01;31:*.war=01;31:*.ear=01;31:*.sar=01;31:*.rar=01;31:*.alz=01;31:*.ace=01;31:*.zoo=01;31:*.cpio=01;31:*.7z=01;31:*.rz=01;31:*.cab=01;31:*.jpg=01;35:*.jpeg=01;35:*.gif=01;35:*.bmp=01;35:*.pbm=01;35:*.pgm=01;35:*.ppm=01;35:*.tga=01;35:*.xbm=01;35:*.xpm=01;35:*.tif=01;35:*.tiff=01;35:*.png=01;35:*.svg=01;35:*.svgz=01;35:*.mng=01;35:*.pcx=01;35:*.mov=01;35:*.mpg=01;35:*.mpeg=01;35:*.m2v=01;35:*.mkv=01;35:*.webm=01;35:*.ogm=01;35:*.mp4=01;35:*.m4v=01;35:*.mp4v=01;35:*.vob=01;35:*.qt=01;35:*.nuv=01;35:*.wmv=01;35:*.asf=01;35:*.rm=01;35:*.rmvb=01;35:*.flc=01;35:*.avi=01;35:*.fli=01;35:*.flv=01;35:*.gl=01;35:*.dl=01;35:*.xcf=01;35:*.xwd=01;35:*.yuv=01;35:*.cgm=01;35:*.emf=01;35:*.ogv=01;35:*.ogx=01;35:*.aac=00;36:*.au=00;36:*.flac=00;36:*.m4a=00;36:*.mid=00;36:*.midi=00;36:*.mka=00;36:*.mp3=00;36:*.mpc=00;36:*.ogg=00;36:*.ra=00;36:*.wav=00;36:*.oga=00;36:*.opus=00;36:*.spx=00;36:*.xspf=00;36:
LC_TELEPHONE=fr_FR.UTF-8
MAIL=/var/mail/trainee
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin
QT_QPA_PLATFORMTHEME=appmenu-qt5
LC_IDENTIFICATION=fr_FR.UTF-8
PWD=/home/trainee
LANG=en_US.UTF-8
LC_MEASUREMENT=fr_FR.UTF-8
SHLVL=1
HOME=/home/trainee
LOGNAME=trainee
SSH_CONNECTION=10.0.2.2 40266 10.0.2.15 22
LESSOPEN=| /usr/bin/lesspipe %s
XDG_RUNTIME_DIR=/run/user/1000
LESSCLOSE=/usr/bin/lesspipe %s %s
LC_TIME=fr_FR.UTF-8
LC_NAME=fr_FR.UTF-8
_=/usr/bin/env

[trainee@centos7 ~]$ env
XDG_SESSION_ID=1
HOSTNAME=centos7.fenestros.loc
SELINUX_ROLE_REQUESTED=
TERM=xterm-256color
SHELL=/bin/bash
HISTSIZE=1000
SSH_CLIENT=10.0.2.2 33896 22
SELINUX_USE_CURRENT_RANGE=
SSH_TTY=/dev/pts/0
LC_ALL=en_GB.UTF-8
USER=trainee
LS_COLORS=rs=0:di=38;5;27:ln=38;5;51:mh=44;38;5;15:pi=40;38;5;11:so=38;5;13:do=38;5;5:bd=48;5;232;38;5;11:cd=48;5;232;38;5;3:or=48;5;232;38;5;9:mi=05;48;5;232;38;5;15:su=48;5;196;38;5;15:sg=48;5;11;38;5;16:ca=48;5;196;38;5;226:tw=48;5;10;38;5;16:ow=48;5;10;38;5;21:st=48;5;21;38;5;15:ex=38;5;34:*.tar=38;5;9:*.tgz=38;5;9:*.arc=38;5;9:*.arj=38;5;9:*.taz=38;5;9:*.lha=38;5;9:*.lz4=38;5;9:*.lzh=38;5;9:*.lzma=38;5;9:*.tlz=38;5;9:*.txz=38;5;9:*.tzo=38;5;9:*.t7z=38;5;9:*.zip=38;5;9:*.z=38;5;9:*.Z=38;5;9:*.dz=38;5;9:*.gz=38;5;9:*.lrz=38;5;9:*.lz=38;5;9:*.lzo=38;5;9:*.xz=38;5;9:*.bz2=38;5;9:*.bz=38;5;9:*.tbz=38;5;9:*.tbz2=38;5;9:*.tz=38;5;9:*.deb=38;5;9:*.rpm=38;5;9:*.jar=38;5;9:*.war=38;5;9:*.ear=38;5;9:*.sar=38;5;9:*.rar=38;5;9:*.alz=38;5;9:*.ace=38;5;9:*.zoo=38;5;9:*.cpio=38;5;9:*.7z=38;5;9:*.rz=38;5;9:*.cab=38;5;9:*.jpg=38;5;13:*.jpeg=38;5;13:*.gif=38;5;13:*.bmp=38;5;13:*.pbm=38;5;13:*.pgm=38;5;13:*.ppm=38;5;13:*.tga=38;5;13:*.xbm=38;5;13:*.xpm=38;5;13:*.tif=38;5;13:*.tiff=38;5;13:*.png=38;5;13:*.svg=38;5;13:*.svgz=38;5;13:*.mng=38;5;13:*.pcx=38;5;13:*.mov=38;5;13:*.mpg=38;5;13:*.mpeg=38;5;13:*.m2v=38;5;13:*.mkv=38;5;13:*.webm=38;5;13:*.ogm=38;5;13:*.mp4=38;5;13:*.m4v=38;5;13:*.mp4v=38;5;13:*.vob=38;5;13:*.qt=38;5;13:*.nuv=38;5;13:*.wmv=38;5;13:*.asf=38;5;13:*.rm=38;5;13:*.rmvb=38;5;13:*.flc=38;5;13:*.avi=38;5;13:*.fli=38;5;13:*.flv=38;5;13:*.gl=38;5;13:*.dl=38;5;13:*.xcf=38;5;13:*.xwd=38;5;13:*.yuv=38;5;13:*.cgm=38;5;13:*.emf=38;5;13:*.axv=38;5;13:*.anx=38;5;13:*.ogv=38;5;13:*.ogx=38;5;13:*.aac=38;5;45:*.au=38;5;45:*.flac=38;5;45:*.mid=38;5;45:*.midi=38;5;45:*.mka=38;5;45:*.mp3=38;5;45:*.mpc=38;5;45:*.ogg=38;5;45:*.ra=38;5;45:*.wav=38;5;45:*.axa=38;5;45:*.oga=38;5;45:*.spx=38;5;45:*.xspf=38;5;45:
MAIL=/var/spool/mail/trainee
PATH=/usr/local/bin:/usr/bin:/usr/local/sbin:/usr/sbin:/home/trainee/.local/bin:/home/trainee/bin
PWD=/home/trainee
LANG=fr_FR.UTF-8
SELINUX_LEVEL_REQUESTED=
HISTCONTROL=ignoredups
SHLVL=1
HOME=/home/trainee
LOGNAME=trainee
SSH_CONNECTION=10.0.2.2 33896 192.168.1.99 22
LESSOPEN=||/usr/bin/lesspipe.sh %s
XDG_RUNTIME_DIR=/run/user/1000
_=/usr/bin/env
OLDPWD=/home/trainee/training

trainee@SLES12SP1:~> env
LESSKEY=/etc/lesskey.bin
NNTPSERVER=news
MANPATH=/usr/local/man:/usr/share/man
XDG_SESSION_ID=1
HOSTNAME=SLES12SP1
XKEYSYMDB=/usr/X11R6/lib/X11/XKeysymDB
HOST=SLES12SP1
TERM=xterm-256color
SHELL=/bin/bash
PROFILEREAD=true
HISTSIZE=1000
SSH_CLIENT=10.0.2.2 46258 22
MORE=-sl
SSH_TTY=/dev/pts/0
LC_ALL=en_GB.UTF-8
USER=trainee
LS_COLORS=no=00:fi=00:di=01;34:ln=00;36:pi=40;33:so=01;35:do=01;35:bd=40;33;01:cd=40;33;01:or=41;33;01:ex=00;32:*.cmd=00;32:*.exe=01;32:*.com=01;32:*.bat=01;32:*.btm=01;32:*.dll=01;32:*.tar=00;31:*.tbz=00;31:*.tgz=00;31:*.rpm=00;31:*.deb=00;31:*.arj=00;31:*.taz=00;31:*.lzh=00;31:*.lzma=00;31:*.zip=00;31:*.zoo=00;31:*.z=00;31:*.Z=00;31:*.gz=00;31:*.bz2=00;31:*.tb2=00;31:*.tz2=00;31:*.tbz2=00;31:*.xz=00;31:*.avi=01;35:*.bmp=01;35:*.fli=01;35:*.gif=01;35:*.jpg=01;35:*.jpeg=01;35:*.mng=01;35:*.mov=01;35:*.mpg=01;35:*.pcx=01;35:*.pbm=01;35:*.pgm=01;35:*.png=01;35:*.ppm=01;35:*.tga=01;35:*.tif=01;35:*.xbm=01;35:*.xpm=01;35:*.dl=01;35:*.gl=01;35:*.wmv=01;35:*.aiff=00;32:*.au=00;32:*.mid=00;32:*.mp3=00;32:*.ogg=00;32:*.voc=00;32:*.wav=00;32:
XNLSPATH=/usr/share/X11/nls
QEMU_AUDIO_DRV=pa
HOSTTYPE=x86_64
FROM_HEADER=
PAGER=less
CSHEDIT=emacs
XDG_CONFIG_DIRS=/etc/xdg
LIBGL_DEBUG=quiet
MINICOM=-c on
MAIL=/var/mail/trainee
PATH=/home/trainee/bin:/usr/local/bin:/usr/bin:/bin:/usr/bin/X11:/usr/games
CPU=x86_64
SSH_SENDS_LOCALE=yes
INPUTRC=/home/trainee/.inputrc
PWD=/home/trainee
LANG=fr_FR.UTF-8
PYTHONSTARTUP=/etc/pythonstart
GPG_TTY=/dev/pts/0
AUDIODRIVER=pulseaudio
QT_SYSTEM_DIR=/usr/share/desktop-data
SHLVL=1
HOME=/home/trainee
ALSA_CONFIG_PATH=/etc/alsa-pulse.conf
SDL_AUDIODRIVER=pulse
LESS_ADVANCED_PREPROCESSOR=no
OSTYPE=linux
LS_OPTIONS=-N --color=tty -T 0
XCURSOR_THEME=DMZ
WINDOWMANAGER=env GNOME_SHELL_SESSION_MODE=sle-classic gnome-session --session sle-classic
G_FILENAME_ENCODING=@locale,UTF-8,ISO-8859-15,CP1252
LESS=-M -I -R
MACHTYPE=x86_64-suse-linux
LOGNAME=trainee
XDG_DATA_DIRS=/usr/share
SSH_CONNECTION=10.0.2.2 46258 10.0.2.15 22
LESSOPEN=lessopen.sh %s
XDG_RUNTIME_DIR=/run/user/1000
NO_AT_BRIDGE=1
LESSCLOSE=lessclose.sh %s %s
G_BROKEN_FILENAMES=1
COLORTERM=1
_=/usr/bin/env
OLDPWD=/home/trainee/training

To run a program, such as xterm in a modified environment the command is:

$ env EDITOR=vim xterm

Bash Shell Options

To view all the options of the bash shell, use the command set:

trainee@debian8:~$ set -o
allexport      	off
braceexpand    	on
emacs          	on
errexit        	off
errtrace       	off
functrace      	off
hashall        	on
histexpand     	on
history        	on
ignoreeof      	off
interactive-comments	on
keyword        	off
monitor        	on
noclobber      	off
noexec         	off
noglob         	off
nolog          	off
notify         	off
nounset        	off
onecmd         	off
physical       	off
pipefail       	off
posix          	off
privileged     	off
verbose        	off
vi             	off
xtrace         	off

trainee@ubuntu1604:~$ set -o
allexport      	off
braceexpand    	on
emacs          	on
errexit        	off
errtrace       	off
functrace      	off
hashall        	on
histexpand     	on
history        	on
ignoreeof      	off
interactive-comments	on
keyword        	off
monitor        	on
noclobber      	off
noexec         	off
noglob         	off
nolog          	off
notify         	off
nounset        	off
onecmd         	off
physical       	off
pipefail       	off
posix          	off
privileged     	off
verbose        	off
vi             	off
xtrace         	off

[trainee@centos7 ~]$ set -o
allexport      	off
braceexpand    	on
emacs          	on
errexit        	off
errtrace       	off
functrace      	off
hashall        	on
histexpand     	on
history        	on
ignoreeof      	off
interactive-comments	on
keyword        	off
monitor        	on
noclobber      	off
noexec         	off
noglob         	off
nolog          	off
notify         	off
nounset        	off
onecmd         	off
physical       	off
pipefail       	off
posix          	off
privileged     	off
verbose        	off
vi             	off
xtrace         	off

trainee@SLES12SP1:~> set -o
allexport      	off
braceexpand    	on
emacs          	on
errexit        	off
errtrace       	off
functrace      	off
hashall        	on
histexpand     	on
history        	on
ignoreeof      	off
interactive-comments	on
keyword        	off
monitor        	on
noclobber      	off
noexec         	off
noglob         	off
nolog          	off
notify         	off
nounset        	off
onecmd         	off
physical       	off
pipefail       	off
posix          	off
privileged     	off
verbose        	off
vi             	off
xtrace         	off

To turn on an option you need to specify which option as an argument to the previous command:

trainee@debian8:~$ set -o allexport
trainee@debian8:~$ set -o
allexport      	on
braceexpand    	on
...

trainee@ubuntu1604:~$ set -o allexport
trainee@ubuntu1604:~$ set -o
allexport      	on
braceexpand    	on
...

[trainee@centos7 ~]$ set -o allexport
[trainee@centos7 ~]$ set -o
allexport      	on
braceexpand    	on
...

trainee@SLES12SP1:~> set -o allexport
trainee@SLES12SP1:~> set -o
allexport      	on
braceexpand    	on
...

To turn off an option, use set with the +o option:

trainee@debian8:~$ set +o allexport
trainee@debian8:~$ set -o
allexport      	off
braceexpand    	on
...

trainee@ubuntu1604:~$ set +o allexport
trainee@ubuntu1604:~$ set -o
allexport      	off
braceexpand    	on
...

[trainee@centos7 ~]$ set +o allexport
[trainee@centos7 ~]$ set -o
allexport      	off
braceexpand    	on
...

trainee@SLES12SP1:~> set +o allexport
trainee@SLES12SP1:~> set -o
allexport      	off
braceexpand    	on
...

These are the most interesting options:

Option	Default value	Description
allexport	off	The shell automatically exports all variables
emacs	on	emacs editing mode
noclobber	off	Simple re-directions do not squash the target file if it exists
noglob	off	Turns off special characters
nounset	off	The shell will return an error if the variable is not set
verbose	off	Echos back the typed command
vi	off	vi editing mode

noclobber

trainee@debian8:~$ set -o noclobber
trainee@debian8:~$ pwd > file
-bash: file: cannot overwrite existing file
trainee@debian8:~$ pwd > file
-bash: file: cannot overwrite existing file
trainee@debian8:~$ pwd >| file
trainee@debian8:~$ set +o noclobber

trainee@ubuntu1604:~$ set -o noclobber
trainee@ubuntu1604:~$ pwd > file
trainee@ubuntu1604:~$ pwd > file
-bash: file: cannot overwrite existing file
trainee@ubuntu1604:~$ pwd >| file
trainee@ubuntu1604:~$ set +o noclobber

[trainee@centos7 ~]$ set -o noclobber
[trainee@centos7 ~]$ pwd > file
-bash: file: cannot overwrite existing file
[trainee@centos7 ~]$ pwd > file
-bash: file: cannot overwrite existing file
[trainee@centos7 ~]$ pwd >| file
[trainee@centos7 ~]$ set +o noclobber

trainee@SLES12SP1:~> set -o noclobber
trainee@SLES12SP1:~> pwd > file
trainee@SLES12SP1:~> pwd > file
-bash: file: cannot overwrite existing file
trainee@SLES12SP1:~> pwd >| file
trainee@SLES12SP1:~> set +o noclobber

Important : Note that the noclobber option can be overidden by using a pipe.

noglob

trainee@debian8:~$ set -o noglob
trainee@debian8:~$ echo *
*
trainee@debian8:~$ set +o noglob
trainee@debian8:~$ echo *
aac abc bca codes Desktop Documents Downloads errorlog file file1 Music Pictures Public Templates training Videos vitext xyz

trainee@ubuntu1604:~$ set -o noglob
trainee@ubuntu1604:~$ echo *
*
trainee@ubuntu1604:~$ set +o noglob
trainee@ubuntu1604:~$ echo *
aac abc bca codes Desktop Documents Downloads errorlog examples.desktop file file1 Music Pictures Public Templates training Videos vitext xyz

[trainee@centos7 ~]$ set -o noglob
[trainee@centos7 ~]$ echo *
*
[trainee@centos7 ~]$ set +o noglob
[trainee@centos7 ~]$ echo *
aac abc bca codes Desktop Documents Downloads errorlog file file1 Music Pictures Public Templates training Videos vitext xyz

trainee@SLES12SP1:~> set -o noglob
trainee@SLES12SP1:~> echo *
*
trainee@SLES12SP1:~> set +o noglob
trainee@SLES12SP1:~> echo *
aac abc bca bin codes Desktop Documents Downloads errorlog file file1 Music Pictures Public public_html Templates training Videos vitext xyz

Important : Note that metacharacters are turned off when the noglob option is set.

nounset

trainee@debian8:~$ set -o nounset
trainee@debian8:~$ echo $FENESTROS
-bash: FENESTROS: unbound variable
trainee@debian8:~$ set +o nounset
trainee@debian8:~$ echo $FENESTROS

trainee@debian8:~$

trainee@ubuntu1604:~$ set -o nounset
trainee@ubuntu1604:~$ echo $FENESTROS
-bash: FENESTROS: unbound variable
trainee@ubuntu1604:~$ set +o nounset
trainee@ubuntu1604:~$ echo $FENESTROS

trainee@ubuntu1604:~$

[trainee@centos7 ~]$ set -o nounset
[trainee@centos7 ~]$ echo $FENESTROS
-bash: FENESTROS: unbound variable
[trainee@centos7 ~]$ set +o nounset
[trainee@centos7 ~]$ echo $FENESTROS

[trainee@centos7 ~]$

trainee@SLES12SP1:~> set -o nounset
trainee@SLES12SP1:~> echo $FENESTROS
-bash: FENESTROS: unbound variable
trainee@SLES12SP1:~> set +o nounset
trainee@SLES12SP1:~> echo $FENESTROS

trainee@SLES12SP1:~>

Important : Note that the inexistant variable $FENESTROS is identified as such when the nounset option is set.

Basic Shell Scripting

Execution

A script is a text file that is read by the system and it's contents executed. There are five ways to execute a script:

By stipulating the shell that will execute the script:

/bin/bash myscript

by a reverse redirection:

/bin/bash < myscript

By calling the script by it's name, provided that the script is executable and that it resides in a directory specified by your path :

myscript

By placing yourself in the directory where the script resides and using one of the two following possibilities :

. myscript et ./myscript

Important: In the first case the script is executed in the parent shell. In the second case the script is executed in a child shell.

Comments in a script are lines starting with #. However, each script starts with a pseudo-comment that informs the system which shell should be used to execute the script:

#!/bin/sh

Since a script in it's simplest form is a list of commands that are sequentially executed, it is often useful to test those command prior to writing the script> Linux has a command that can help you debug a future script. The script command can be used to generate a log file, called typescript, that contains a record of everything occurred on standard output. To exit the recording mode, use exit:

trainee@debian8:~$ script
Script started, file is typescript
trainee@debian8:~$ pwd
/home/trainee
trainee@debian8:~$ ls
aac  bca    Desktop    Downloads  fichier1  file   Music     Public     training    Videos  xyz
abc  codes  Documents  errorlog   fichier2  file1  Pictures  Templates  typescript  vitext
trainee@debian8:~$ exit
exit
Script done, file is typescript
trainee@debian8:~$ cat typescript 
Script started on Tue 29 Nov 2016 02:56:33 GMT
trainee@debian8:~$ pwd
/home/trainee
trainee@debian8:~$ ls
aac  bca    Desktop    Downloads  fichier1  file   Music     Public     training    Videos  xyz
abc  codes  Documents  errorlog   fichier2  file1  Pictures  Templates  typescript  vitext
trainee@debian8:~$ exit
exit

Script done on Tue 29 Nov 2016 02:56:44 GMT

trainee@ubuntu1604:~$ script
Script started, file is typescript
trainee@ubuntu1604:~$ pwd
/home/trainee
trainee@ubuntu1604:~$ ls
aac  codes      Downloads         fichier1  file1     Public     typescript  xyz
abc  Desktop    errorlog          fichier2  Music     Templates  Videos
bca  Documents  examples.desktop  file      Pictures  training   vitext
trainee@ubuntu1604:~$ exit
exit
Script done, file is typescript
trainee@ubuntu1604:~$ cat typescript 
Script started on Tue 29 Nov 2016 03:57:47 CET
trainee@ubuntu1604:~$ pwd
/home/trainee
trainee@ubuntu1604:~$ ls
aac  codes      Downloads         fichier1  file1     Public     typescript  xyz
abc  Desktop    errorlog          fichier2  Music     Templates  Videos
bca  Documents  examples.desktop  file      Pictures  training   vitext
trainee@ubuntu1604:~$ exit
exit

Script done on Tue 29 Nov 2016 03:57:58 CET

[trainee@centos7 ~]$ script
Script started, file is typescript
[trainee@centos7 ~]$ pwd
/home/trainee
[trainee@centos7 ~]$ ls
aac  bca    Desktop    Downloads  fichier1  file   Music     Public     training    Videos  xyz
abc  codes  Documents  errorlog   fichier2  file1  Pictures  Templates  typescript  vitext
[trainee@centos7 ~]$ exit
exit
Script done, file is typescript
[trainee@centos7 ~]$ cat typescript 
Script started on Tue 29 Nov 2016 03:58:33 CET
[trainee@centos7 ~]$ pwd
/home/trainee
[trainee@centos7 ~]$ ls
aac  bca    Desktop    Downloads  fichier1  file   Music     Public     training    Videos  xyz
abc  codes  Documents  errorlog   fichier2  file1  Pictures  Templates  typescript  vitext
[trainee@centos7 ~]$ exit
exit

Script done on Tue 29 Nov 2016 03:58:40 CET

trainee@SLES12SP1:~> script
Script started, file is typescript
trainee@SLES12SP1:~> pwd
/home/trainee
trainee@SLES12SP1:~> ls
aac  bin      Documents  fichier1  file1     Public       training    vitext
abc  codes    Downloads  fichier2  Music     public_html  typescript  xyz
bca  Desktop  errorlog   file      Pictures  Templates    Videos
trainee@SLES12SP1:~> exit
exit
Script done, file is typescript
trainee@SLES12SP1:~> cat typescript 
Script started on Tue 29 Nov 2016 03:59:24 CET
trainee@SLES12SP1:~> pwd
/home/trainee
trainee@SLES12SP1:~> ls
aac  bin      Documents  fichier1  file1     Public       training    vitext
abc  codes    Downloads  fichier2  Music     public_html  typescript  xyz
bca  Desktop  errorlog   file      Pictures  Templates    Videos
trainee@SLES12SP1:~> exit
exit

Script done on Tue 29 Nov 2016 03:59:31 CET

Lets start by creating a simple script called myscript:

$ vi myscript [Enter]

Edit the file as follows:

pwd
ls

Important: Note that in the above example, the script does not start with a pseudo-comment. As a result, the script will be executed by the shell of the user that invokes it unless a different shell is specified.

Save the file and use the five ways to execute it.

As an argument de /bin/bash:

trainee@debian8:~$ vi myscript
trainee@debian8:~$ /bin/bash myscript
/home/trainee
aac  codes	Downloads  fichier2  myscript	Public	   typescript  xyz
abc  Desktop	errorlog   file      Music	Templates  Videos
bca  Documents	fichier1   file1     Pictures	training   vitext

trainee@ubuntu1604:~$ vi myscript
trainee@ubuntu1604:~$ /bin/bash myscript
/home/trainee
aac  codes	Downloads	  fichier1  file1      Pictures   training    vitext
abc  Desktop	errorlog	  fichier2  myscript  Public	  typescript  xyz
bca  Documents	examples.desktop  file	    Music      Templates  Videos

[trainee@centos7 ~]$ vi myscript
[trainee@centos7 ~]$ /bin/bash myscript
/home/trainee
aac  codes	Downloads  fichier2  myscript	Public	   typescript  xyz
abc  Desktop	errorlog   file      Music	Templates  Videos
bca  Documents	fichier1   file1     Pictures	training   vitext

trainee@SLES12SP1:~> vi myscript
trainee@SLES12SP1:~> /bin/bash myscript
/home/trainee
aac  bin      Documents  fichier1  file1      Pictures	   Templates   Videos
abc  codes    Downloads  fichier2  myscript  Public	   training    vitext
bca  Desktop  errorlog	 file	   Music      public_html  typescript  xyz

Using a redirection:

trainee@debian8:~$ /bin/bash < myscript
/home/trainee
aac  codes	Downloads  fichier2  myscript	Public	   typescript  xyz
abc  Desktop	errorlog   file      Music	Templates  Videos
bca  Documents	fichier1   file1     Pictures	training   vitext

trainee@ubuntu1604:~$ /bin/bash < myscript
/home/trainee
aac  codes	Downloads	  fichier1  file1      Pictures   training    vitext
abc  Desktop	errorlog	  fichier2  myscript  Public	  typescript  xyz
bca  Documents	examples.desktop  file	    Music      Templates  Videos

[trainee@centos7 ~]$ /bin/bash < myscript
/home/trainee
aac  codes	Downloads  fichier2  myscript	Public	   typescript  xyz
abc  Desktop	errorlog   file      Music	Templates  Videos
bca  Documents	fichier1   file1     Pictures	training   vitext

trainee@SLES12SP1:~> /bin/bash < myscript
/home/trainee
aac  bin      Documents  fichier1  file1      Pictures	   Templates   Videos
abc  codes    Downloads  fichier2  myscript  Public	   training    vitext
bca  Desktop  errorlog	 file	   Music      public_html  typescript  xyz

In order to be able to call the script by it's name from another directory, such as /tmp, you need to move the script into the /home/trainee/bin directory and make it executable. Note that in this case, the the value of the environmental variable $PATH should contain a reference to /home/trainee/bin:

trainee@debian8:~$ echo $PATH
/usr/local/bin:/usr/bin:/bin:/usr/local/games:/usr/games

trainee@ubuntu1604:~$ echo $PATH
/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin

[trainee@centos7 ~]$ echo $PATH
/usr/local/bin:/usr/bin:/usr/local/sbin:/usr/sbin:/home/trainee/.local/bin:/home/trainee/bin

trainee@SLES12SP1:~> echo $PATH
/home/trainee/bin:/usr/local/bin:/usr/bin:/bin:/usr/bin/X11:/usr/games

As you can see, in the case of Debian and Ubuntu, this is not the case. The reason for this becomes apparent when viewing the contents of the .profile file in /home/trainee:

trainee@debian8:~$ cat .profile
# ~/.profile: executed by the command interpreter for login shells.
...
# set PATH so it includes user's private bin if it exists
if [ -d "$HOME/bin" ] ; then
    PATH="$HOME/bin:$PATH"
fi

trainee@ubuntu1604:~$ cat .profile
# ~/.profile: executed by the command interpreter for login shells.
...
# set PATH so it includes user's private bin if it exists
if [ -d "$HOME/bin" ] ; then
    PATH="$HOME/bin:$PATH"
fi

As you can see PATH is set so it includes the user's private bin only if the directory exists:

# set PATH so it includes user's private bin if it exists
if [ -d "$HOME/bin" ] ; then
    PATH="$HOME/bin:$PATH"
fi

To fix the value of the PATH variable, create the $HOME/bin directory and re-load the .profile file:

trainee@debian8:~$ mkdir bin
trainee@debian8:~$ source .profile
trainee@debian8:~$ echo $PATH
/home/trainee/bin:/usr/local/bin:/usr/bin:/bin:/usr/local/games:/usr/games

trainee@ubuntu1604:~$ mkdir bin
trainee@ubuntu1604:~$ source .profile 
trainee@ubuntu1604:~$ echo $PATH
/home/trainee/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin

In the case of RHEL/CentOS, even though PATH contains $HOME/bin, the directory is not present:

[trainee@centos7 ~]$ ls
aac  codes      Downloads  fichier2  myscript  Public     typescript  xyz
abc  Desktop    errorlog   file      Music      Templates  Videos
bca  Documents  fichier1   file1     Pictures   training   vitext

So you need to create the directory:

[trainee@centos7 ~]$ mkdir bin

Now you need to move the script to $HOME/bin and make it executable:

trainee@debian8:~$ mv myscript ~/bin
trainee@debian8:~$ chmod u+x ~/bin/myscript

trainee@ubuntu1604:~$ mv myscript ~/bin
trainee@ubuntu1604:~$ chmod u+x ~/bin/myscript

[trainee@centos7 ~]$ mv myscript ~/bin
[trainee@centos7 ~]$ chmod u+x ~/bin/myscript

trainee@SLES12SP1:~> mv myscript ~/bin
trainee@SLES12SP1:~> chmod u+x ~/bin/myscript

Move to /tmp and can call the script by just using it's name:

trainee@debian8:/tmp$ myscript
/tmp
hsperfdata_root  pulse-PKdhtXMmr18n

trainee@ubuntu1604:/tmp$ myscript
/tmp
hsperfdata_root
systemd-private-2596faf2be00473d9dc6da53af5711d5-colord.service-K4xRp2
systemd-private-2596faf2be00473d9dc6da53af5711d5-rtkit-daemon.service-iKio6G
systemd-private-2596faf2be00473d9dc6da53af5711d5-systemd-timesyncd.service-AlOq91

[trainee@centos7 tmp]$ myscript
/tmp
hsperfdata_root  systemd-private-e526abcf335b40949dfc725f28456502-cups.service-u0xGiL

trainee@SLES12SP1:/tmp> myscript
/tmp
hsperfdata_root
inode
managera1411267841657715235client
managera3336001029897679475server
managera4847938942232964844client
managera5050357016347721452server
systemd-private-04f820fa26c745be8ddba814c6292f21-rtkit-daemon.service-o4lKP5
systemicontmp5578677472245134133dat
systemicontmp7082392205020802884dat

Now move back to ~/bin and use the following two commands to execute myscript:

./myscript
. myscript

trainee@debian8:/tmp$ cd ~/bin
trainee@debian8:~/bin$ ./myscript
/home/trainee/bin
myscript
trainee@debian8:~/bin$ . myscript
/home/trainee/bin
myscript

trainee@ubuntu1604:/tmp$ cd ~/bin
trainee@ubuntu1604:~/bin$ ./myscript
/home/trainee/bin
myscript
trainee@ubuntu1604:~/bin$ . myscript
/home/trainee/bin
myscript

[trainee@centos7 tmp]$ cd ~/bin
[trainee@centos7 bin]$ ./myscript 
/home/trainee/bin
myscript
[trainee@centos7 bin]$ . myscript 
/home/trainee/bin
myscript

trainee@SLES12SP1:/tmp> cd ~/bin
trainee@SLES12SP1:~/bin> ./myscript
/home/trainee/bin
myscript
trainee@SLES12SP1:~/bin> . myscript
/home/trainee/bin
myscript

To do: Note the difference in the output of these two commands and explain that difference.

The read command

The read command reads the standard input and stores the information in the variables that are specified as arguments. The separator between fields is a space, a tabultaion or a carriage return:

trainee@debian8:~/bin$ read var1 var2 var3 var4
fenestros edu is great!
trainee@debian8:~/bin$ echo $var1
fenestros
trainee@debian8:~/bin$ echo $var2
edu
trainee@debian8:~/bin$ echo $var3
is
trainee@debian8:~/bin$ echo $var4
great!

trainee@ubuntu1604:~/bin$ read var1 var2 var3 var4
fenestros edu is great!
trainee@ubuntu1604:~/bin$ echo $var1
fenestros
trainee@ubuntu1604:~/bin$ echo $var2
edu
trainee@ubuntu1604:~/bin$ echo $var3
is
trainee@ubuntu1604:~/bin$ echo $var4
great!

[trainee@centos7 bin]$ read var1 var2 var3 var4
fenestros edu is great!
[trainee@centos7 bin]$ echo $var1
fenestros
[trainee@centos7 bin]$ echo $var2
edu
[trainee@centos7 bin]$ echo $var3
is
[trainee@centos7 bin]$ echo $var4
great!

trainee@SLES12SP1:~/bin> read var1 var2 var3 var4
fenestros edu is great!
trainee@SLES12SP1:~/bin> echo $var1
fenestros
trainee@SLES12SP1:~/bin> echo $var2
edu
trainee@SLES12SP1:~/bin> echo $var3
is
trainee@SLES12SP1:~/bin> echo $var4
great!

Important: Note that each field has been placed in a seperate variable. Note also that by convention, user declared variables are in lower case in order to distinguish them from system variables.

trainee@debian8:~/bin$ read var1 var2
fenestros edu is great!
trainee@debian8:~/bin$ echo $var1
fenestros
trainee@debian8:~/bin$ echo $var2
edu is great!

trainee@ubuntu1604:~/bin$ read var1 var2
fenestros edu is great!
trainee@ubuntu1604:~/bin$ echo $var1
fenestros
trainee@ubuntu1604:~/bin$ echo $var2
edu is great!

[trainee@centos7 bin]$ read var1 var2
fenestros edu is great!
[trainee@centos7 bin]$ echo $var1
fenestros
[trainee@centos7 bin]$ echo $var2
edu is great!

trainee@SLES12SP1:~/bin> read var1 var2
fenestros edu is great!
trainee@SLES12SP1:~/bin> echo $var1
fenestros
trainee@SLES12SP1:~/bin> echo $var2
edu is great!

Important: Note that in this case, $var2 contains three fields.

Code de retour

The contents of a variable can also be empty:

trainee@debian8:~/bin$ read var

↵ Enter

trainee@debian8:~/bin$ echo $?
0
trainee@debian8:~/bin$ echo $var

trainee@debian8:~/bin$

trainee@ubuntu1604:~/bin$ read var

↵ Enter

trainee@ubuntu1604:~/bin$ echo $?
0
trainee@ubuntu1604:~/bin$ echo $var

trainee@ubuntu1604:~/bin$

[trainee@centos7 bin]$ read var

↵ Enter

[trainee@centos7 bin]$ echo $?
0
[trainee@centos7 bin]$ echo $var

[trainee@centos7 bin]$

trainee@SLES12SP1:~/bin> read var

↵ Enter

trainee@SLES12SP1:~/bin> echo $?
0
trainee@SLES12SP1:~/bin> echo $var

trainee@SLES12SP1:~/bin>

But not null:

trainee@debian8:~/bin$ read var

Ctrl+D

trainee@debian8:~/bin$ echo $?
1
trainee@debian8:~/bin$ echo $var

trainee@debian8:~/bin$

trainee@ubuntu1604:~/bin$ read var

Ctrl+D

trainee@ubuntu1604:~/bin$ echo $?
1
trainee@ubuntu1604:~/bin$ echo $var

trainee@ubuntu1604:~/bin$

[trainee@centos7 bin]$ read var

Ctrl+D

[trainee@centos7 bin]$ echo $?
1
[trainee@centos7 bin]$ echo $var

[trainee@centos7 bin]$

trainee@SLES12SP1:~/bin> read var

Ctrl+D

trainee@SLES12SP1:~/bin> echo $?
1
trainee@SLES12SP1:~/bin> echo $var

trainee@SLES12SP1:~/bin>

The IFS Variable

The IFS variable contains the default separator characters: SpaceBar, Tab ⇆ and ↵ Enter:

trainee@debian8:~/bin$ echo "$IFS" | od -c
0000000      \t  \n  \n
0000004

trainee@ubuntu1604:~/bin$ echo "$IFS" | od -c
0000000      \t  \n  \n
0000004

[trainee@centos7 bin]$ echo "$IFS" | od -c
0000000      \t  \n  \n
0000004

trainee@SLES12SP1:~/bin> echo "$IFS" | od -c
0000000      \t  \n  \n
0000004

Important: The od command (Octal Dump) returns the contents of a file in octal format. The -c switch prints to standard output any ASCII characters or backslashes contained within the file.

It is possible to change the contents of this variable:

trainee@debian8:~/bin$ OLDIFS="$IFS"
trainee@debian8:~/bin$ IFS=":"
trainee@debian8:~/bin$ echo "$IFS" | od -c
0000000   :  \n
0000002

trainee@ubuntu1604:~/bin$ OLDIFS="$IFS"
trainee@ubuntu1604:~/bin$ IFS=":"
trainee@ubuntu1604:~/bin$ echo "$IFS" | od -c
0000000   :  \n
0000002

[trainee@centos7 bin]$ OLDIFS="$IFS"
[trainee@centos7 bin]$ IFS=":"
[trainee@centos7 bin]$ echo "$IFS" | od -c
0000000   :  \n
0000002

trainee@SLES12SP1:~/bin> OLDIFS="$IFS"
trainee@SLES12SP1:~/bin> IFS=":"
trainee@SLES12SP1:~/bin> echo "$IFS" | od -c
0000000   :  \n
0000002

Now test the new configuration:

trainee@debian8:~/bin$ read var1 var2 var3
fenestros:edu is:great!
trainee@debian8:~/bin$ echo $var1
fenestros
trainee@debian8:~/bin$ echo $var2
edu is
trainee@debian8:~/bin$ echo $var3
great!

trainee@ubuntu1604:~/bin$ read var1 var2 var3
fenestros:edu is:great!
trainee@ubuntu1604:~/bin$ echo $var1
fenestros
trainee@ubuntu1604:~/bin$ echo $var2
edu is
trainee@ubuntu1604:~/bin$ echo $var3
great!

[trainee@centos7 bin]$ read var1 var2 var3
fenestros:edu is:great!
[trainee@centos7 bin]$ echo $var1
fenestros
[trainee@centos7 bin]$ echo $var2
edu is
[trainee@centos7 bin]$ echo $var3
great!

trainee@SLES12SP1:~/bin> read var1 var2 var3
fenestros:edu is:great!
trainee@SLES12SP1:~/bin> echo $var1
fenestros
trainee@SLES12SP1:~/bin> echo $var2
edu is
trainee@SLES12SP1:~/bin> echo $var3
great!

Restore the old value of IFS before proceeding further: IFS=“$OLDIFS”

trainee@debian8:~/bin$ IFS="$OLDIFS"
trainee@debian8:~/bin$ echo "$IFS" | od -c
0000000      \t  \n  \n
0000004

trainee@ubuntu1604:~/bin$ IFS="$OLDIFS"
trainee@ubuntu1604:~/bin$ echo "$IFS" | od -c
0000000      \t  \n  \n
0000004

[trainee@centos7 bin]$ IFS="$OLDIFS"
[trainee@centos7 bin]$ echo "$IFS" | od -c
0000000      \t  \n  \n
0000004

trainee@SLES12SP1:~/bin> IFS="$OLDIFS"
trainee@SLES12SP1:~/bin> echo "$IFS" | od -c
0000000      \t  \n  \n
0000004

The test Command

The test command uses two forms:

test expression

[SpaceBarexpressionSpaceBar]

Testing Files

Test	Description
-f file	Returns true if file is an ordinary file
-d file	Returns true if file is a directory
-r file	Returns true if user can read file
-w file	Returns true if user can write file
-x file	Returns true if user can execute file
-e file	Returns true if file exists
-s file	Returns true if file is not empty
file1 -nt file2	Returns true if file1 is newer than file2
file1 -ot file2	Returns true if file1 is older than file2
file1 -ef file2	Returns true if file1 is identical to file2

LAB #1

Test whether the a100 file is an ordinary file:

trainee@debian8:~/bin$ cd ../training/
trainee@debian8:~/training$ test -f a100
trainee@debian8:~/training$ echo $? 
0
trainee@debian8:~/training$ [ -f a100 ]
trainee@debian8:~/training$ echo $? 
0

trainee@ubuntu1604:~/bin$ cd ../training/
trainee@ubuntu1604:~/training$ test -f a100
trainee@ubuntu1604:~/training$ echo $? 
0
trainee@ubuntu1604:~/training$ [ -f a100 ]
trainee@ubuntu1604:~/training$ echo $? 
0

[trainee@centos7 bin]$ cd ../training/
[trainee@centos7 training]$ test -f a100
[trainee@centos7 training]$ echo $? 
0
[trainee@centos7 training]$ [ -f a100 ]
[trainee@centos7 training]$ echo $? 
0

trainee@SLES12SP1:~/bin> cd ../training/
trainee@SLES12SP1:~/training> test -f a100
trainee@SLES12SP1:~/training> echo $? 
0
trainee@SLES12SP1:~/training> [ -f a100 ]
trainee@SLES12SP1:~/training> echo $? 
0

Important: The value contained in $? is 0. This indicates true.

Test whether the a101 file is an ordinary file:

trainee@debian8:~/training$ [ -f a101 ]
trainee@debian8:~/training$ echo $?
1

trainee@ubuntu1604:~/training$ [ -f a101 ]
trainee@ubuntu1604:~/training$ echo $?
1

[trainee@centos7 training]$ [ -f a101 ]
[trainee@centos7 training]$ echo $?
1

trainee@SLES12SP1:~/training> [ -f a101 ]
trainee@SLES12SP1:~/training> echo $?
1

Important: The value contained in $? is 1. This indicates false. This is obvious since a101 does not exist.

Test whether /home/trainee/training is a directory:

trainee@debian8:~/training$ [ -d /home/trainee/training ]
trainee@debian8:~/training$ echo $?
0

trainee@ubuntu1604:~/training$ [ -d /home/trainee/training ]
trainee@ubuntu1604:~/training$ echo $?
0

[trainee@centos7 training]$ [ -d /home/trainee/training ]
[trainee@centos7 training]$ echo $?
0

trainee@SLES12SP1:~/training> [ -d /home/trainee/training ]
trainee@SLES12SP1:~/training> echo $?
0

Important: The value contained in $? is 0. This indicates true.

Testing Strings

Test	Description
-n string	Returns true if string is not zero in length
-z string	Returns true if string is zero in length
string1 = string2	Returns true if string1 is equal to string2
string1 != string2	Returns true if string1 is different to string2
string1	Returns true if string1 is not empty

LAB #2

Test whether two strings are indentical:

trainee@debian8:~/training$ string1="root"
trainee@debian8:~/training$ string2="fenestros"
trainee@debian8:~/training$ [ $string1 = $string2 ]
trainee@debian8:~/training$ echo $?
1

trainee@ubuntu1604:~/training$ string1="root"
trainee@ubuntu1604:~/training$ string2="fenestros"
trainee@ubuntu1604:~/training$ [ $string1 = $string2 ]
trainee@ubuntu1604:~/training$ echo $?
1

[trainee@centos7 training]$ string1="root"
[trainee@centos7 training]$ string2="fenestros"
[trainee@centos7 training]$ [ $string1 = $string2 ]
[trainee@centos7 training]$ echo $?
1

trainee@SLES12SP1:~/training> string1="root"
trainee@SLES12SP1:~/training> string2="fenestros"
trainee@SLES12SP1:~/training> [ $string1 = $string2 ]
trainee@SLES12SP1:~/training> echo $?
1

Important: The value contained in $? is 1. This indicates false.

Test if string1 is not zero in length:

trainee@debian8:~/training$ [ -n $string1 ]
trainee@debian8:~/training$ echo $?
0

trainee@ubuntu1604:~/training$ [ -n $string1 ]
trainee@ubuntu1604:~/training$ echo $?
0

[trainee@centos7 training]$ [ -n $string1 ]
[trainee@centos7 training]$ echo $?
0

trainee@SLES12SP1:~/training> [ -n $string1 ]
trainee@SLES12SP1:~/training> echo $?
0

Important: The value contained in $? is 0. This indicates true.

Test if string1 is is zero in length:

trainee@debian8:~/training$ [ -z $string1 ]
trainee@debian8:~/training$ echo $?
1

trainee@ubuntu1604:~/training$ [ -z $string1 ]
trainee@ubuntu1604:~/training$ echo $?
1

[trainee@centos7 training]$ [ -z $string1 ]
[trainee@centos7 training]$ echo $?
1

trainee@SLES12SP1:~/training> [ -z $string1 ]
trainee@SLES12SP1:~/training> echo $?
1

Important: The value contained in $? is 1. This indicates false.

Testing Numbers

Test	Description
value1 -eq value2	Returns true if value1 is equal to value2
value1 -ne value2	Returns true if value1 is not equal to value2
value1 -lt value2	Returns true if value1 is less than value2
value1 -le value2	Returns true if value1 is less than or equal to value2
value1 -gt value2	Returns true if value1 is greater than value2
value1 -ge value2	Returns true if value1 is greater than or equal to value2

LAB #3

Compare the two numbers value1 and value2 :

trainee@debian8:~/training$ read value1
35
trainee@debian8:~/training$ read value2
23
trainee@debian8:~/training$ [ $value1 -lt $value2 ]
trainee@debian8:~/training$ echo $?
1
trainee@debian8:~/training$ [ $value2 -lt $value1 ]
trainee@debian8:~/training$ echo $?
0
trainee@debian8:~/training$ [ $value2 -eq $value1 ]
trainee@debian8:~/training$ echo $?
1

trainee@ubuntu1604:~/training$ read value1
35
trainee@ubuntu1604:~/training$ read value2
23
trainee@ubuntu1604:~/training$ [ $value1 -lt $value2 ]
trainee@ubuntu1604:~/training$ echo $?
1
trainee@ubuntu1604:~/training$ [ $value2 -lt $value1 ]
trainee@ubuntu1604:~/training$ echo $?
0
trainee@ubuntu1604:~/training$ [ $value2 -eq $value1 ]
trainee@ubuntu1604:~/training$ echo $?
1

[trainee@centos7 training]$ read value1
35
[trainee@centos7 training]$ read value2
23
[trainee@centos7 training]$ [ $value1 -lt $value2 ]
[trainee@centos7 training]$ echo $?
1
[trainee@centos7 training]$ [ $value2 -lt $value1 ]
[trainee@centos7 training]$ echo $?
0
[trainee@centos7 training]$ [ $value2 -eq $value1 ]
[trainee@centos7 training]$ echo $?
1

trainee@SLES12SP1:~/training> read value1
35
trainee@SLES12SP1:~/training> read value2
23
trainee@SLES12SP1:~/training> [ $value1 -lt $value2 ]
trainee@SLES12SP1:~/training> echo $?
1
trainee@SLES12SP1:~/training> [ $value2 -lt $value1 ]
trainee@SLES12SP1:~/training> echo $?
0
trainee@SLES12SP1:~/training> [ $value2 -eq $value1 ]
trainee@SLES12SP1:~/training> echo $?
1

Expressions

Test	Description
!expression	Returns true if expression is false
expression1 -a expression2	Represents a logical OR between expression1 and expression2
expression1 -o expression2	Represents a logical AND between expression1 and expression2
$expression$	Parenthesis let you group together expressions

LAB #4

Test if $file is not a directory:

trainee@debian8:~/training$ file=a1OO
trainee@debian8:~/training$ [ ! -d $file ]
trainee@debian8:~/training$ echo $?
0

trainee@ubuntu1604:~/training$ file=a1OO
trainee@ubuntu1604:~/training$ [ ! -d $file ]
trainee@ubuntu1604:~/training$ echo $?
0

[trainee@centos7 training]$ file=a1OO
[trainee@centos7 training]$ [ ! -d $file ]
[trainee@centos7 training]$ echo $?
0

trainee@SLES12SP1:~/training> file=a1OO
trainee@SLES12SP1:~/training> [ ! -d $file ]
trainee@SLES12SP1:~/training> echo $?
0

Test if $directory is a directory and if trainee can cd into it:

trainee@debian8:~/training$ directory=/usr
trainee@debian8:~/training$ [ -d $directory -a -x $directory ]
trainee@debian8:~/training$ echo $?
0

trainee@ubuntu1604:~/training$ directory=/usr
trainee@ubuntu1604:~/training$ [ -d $directory -a -x $directory ]
trainee@ubuntu1604:~/training$ echo $?
0

[trainee@centos7 training]$ directory=/usr
[trainee@centos7 training]$ [ -d $directory -a -x $directory ]
[trainee@centos7 training]$ echo $?
0

trainee@SLES12SP1:~/training> directory=/usr
trainee@SLES12SP1:~/training> [ -d $directory -a -x $directory ]
trainee@SLES12SP1:~/training> echo $?
0

Test if trainee has the write permission for the a100 file and test if /usr is a directory or test if /tmp is a directory:

trainee@debian8:~/training$ [ -w a100 -a \( -d /usr -o -d /tmp \) ]
trainee@debian8:~/training$ echo $?
0

trainee@ubuntu1604:~/training$ [ -w a100 -a \( -d /usr -o -d /tmp \) ]
trainee@ubuntu1604:~/training$ echo $?
0

[trainee@centos7 training]$ [ -w a100 -a \( -d /usr -o -d /tmp \) ]
[trainee@centos7 training]$ echo $?
0

trainee@SLES12SP1:~/training> [ -w a100 -a \( -d /usr -o -d /tmp \) ]
trainee@SLES12SP1:~/training> echo $?
0

Testing the User Environment

Test	Description
-o option	Returns true if the shell option “option” is on

LAB #5

trainee@debian8:~/training$ [ -o allexport ]
trainee@debian8:~/training$ echo $?
1

trainee@ubuntu1604:~/training$ [ -o allexport ]
trainee@ubuntu1604:~/training$ echo $?
1

[trainee@centos7 training]$ [ -o allexport ]
[trainee@centos7 training]$ echo $?
1

trainee@SLES12SP1:~/training> [ -o allexport ]
trainee@SLES12SP1:~/training> echo $?
1

The [[ expression ]] Command

The [[SpaceBarexpressionSpaceBar]] command is an improved test command with some minor changes to syntax:

Test	Description
expression1 && expression2	Represents a logical OR between expression1 and expression2
expression1 \|\| expression2	Represents a logical AND between expression1 and expression2
(expression)	Parenthesis let you group together expressions

and some additional operators :

Test	Description
string = model	Returns true if string corresponds to model
string != model	Returns true if string does not correspond to model
string1 < string2	Returns true if string1 is lexicographically before string2
string1 > string2	Returns true if string1 is lexicographically after string2

LAB #6

Test if trainee has the write permission for the a100 file and test if /usr is a directory or test if /tmp is a directory:

trainee@debian8:~/training$ [[ -w a100 && ( -d /usr || -d /tmp ) ]]
trainee@debian8:~/training$ echo $?
0

trainee@ubuntu1604:~/training$ [[ -w a100 && ( -d /usr || -d /tmp ) ]]
trainee@ubuntu1604:~/training$ echo $?
0

[trainee@centos7 training]$ [[ -w a100 && ( -d /usr || -d /tmp ) ]]
[trainee@centos7 training]$ echo $?
0

trainee@SLES12SP1:~/training> [[ -w a100 && ( -d /usr || -d /tmp ) ]]
trainee@SLES12SP1:~/training> echo $?
0

Shell Operators

Operator	Description
Command1 && Command2	Command2 is executed if the exit code of Command1 is zero
Command1 \|\| Command2	Command2 is executed is the exit code of Command1 is not zero

LAB #7

trainee@debian8:~/training$ [[ -d /root ]] && echo "The root directory exists"
The root directory exists
trainee@debian8:~/training$ [[ -d /root ]] || echo "The root directory exists"
trainee@debian8:~/training$

trainee@ubuntu1604:~/training$ [[ -d /root ]] && echo "The root directory exists"
The root directory exists
trainee@ubuntu1604:~/training$ [[ -d /root ]] || echo "The root directory exists"
trainee@ubuntu1604:~/training$

[trainee@centos7 training]$ [[ -d /root ]] && echo "The root directory exists"
The root directory exists
[trainee@centos7 training]$ [[ -d /root ]] || echo "The root directory exists"
[trainee@centos7 training]$

trainee@SLES12SP1:~/training> [[ -d /root ]] && echo "The root directory exists"
The root directory exists
trainee@SLES12SP1:~/training> [[ -d /root ]] || echo "The root directory exists"
trainee@SLES12SP1:~/training>

The expr Command

Theexpr command's syntax is as follows :

expr SpaceBar number1 SpaceBar operator SpaceBar number2 SpaceBar

expr Tab ⇆ number1 Tab operator Tab ⇆ number2 ↵ Enter

expr SpaceBar string SpaceBar : SpaceBar regular_expression SpaceBar

expr Tab ⇆ string Tab ⇆ : Tab ⇆ regular_expression ↵ Enter

Maths

Operator	Description
+	Addition
-	Subtraction
\*	Multiplication
/	Division
%	Modulo
	Parentheses

Comparisons

Operator	Description
\<	Less than
\<=	Less than or equal to
\>	Greater then
\>=	Greater then or equal to
=	Equal to
!=	Not equal to

Logic

Operator	Description
\\|	Logical OR
\&	Logical AND

LAB #8

Add two to the value of $x:

trainee@debian8:~/training$ x=2
trainee@debian8:~/training$ expr $x + 2
4

trainee@ubuntu1604:~/training$ x=2
trainee@ubuntu1604:~/training$ expr $x + 2
4

[trainee@centos7 training]$ x=2
[trainee@centos7 training]$ expr $x + 2
4

trainee@SLES12SP1:~/training> x=2
trainee@SLES12SP1:~/training> expr $x + 2
4

If the surrounding spaces are removed, the result is completely different:

trainee@debian8:~/training$ expr $x+2
2+2

trainee@ubuntu1604:~/training$ expr $x+2
2+2

[trainee@centos7 training]$ expr $x+2
2+2

trainee@SLES12SP1:~/training> expr $x+2
2+2

Certain operators need to be protected:

trainee@debian8:~/training$ expr $x * 2
expr: syntax error
trainee@debian8:~/training$ expr $x \* 2
4

trainee@ubuntu1604:~/training$ expr $x * 2
expr: syntax error
trainee@ubuntu1604:~/training$ expr $x \* 2
4

[trainee@centos7 training]$ expr $x * 2
expr: syntax error
[trainee@centos7 training]$ expr $x \* 2
4

trainee@SLES12SP1:~/training> expr $x * 2
expr: syntax error
trainee@SLES12SP1:~/training> expr $x \* 2
4

Now put the result of a calculation in a variable:

trainee@debian8:~/training$ resultat=`expr $x + 10`
trainee@debian8:~/training$ echo $resultat
12

trainee@ubuntu1604:~/training$ resultat=`expr $x + 10`
trainee@ubuntu1604:~/training$ echo $resultat
12

[trainee@centos7 training]$ resultat=`expr $x + 10`
[trainee@centos7 training]$ echo $resultat
12

trainee@SLES12SP1:~/training> resultat=`expr $x + 10`
trainee@SLES12SP1:~/training> echo $resultat
12

The let Command

The let command is equivalent to ((expression)). The ((expression)) command provides the following additional features when compared with the expr command :

greater number of operators,
no need for spaces or tabulations between arguments,
no need to prefix variables with the $ character,
the shell's special characters do not need to be escaped,
variables are defined directly in the command,
faster execution time.

Maths

Operator	Description
+	Addition
-	Subtraction
*	Multiplication
/	Division
%	Modulo
^	Power

Comparisons

Operator	Description
<	Less than
<=	Less than or equal to
>	Greater then
>=	Greater then or equal to
==	Equal
!=	Not Equal

Logic

Operator	Description
&&	Logical AND
\|\|	Logical OR
!	Logical negation

Binary

Opérateur	Description
~	Binary negation
>>	décalage binaire à droite
<<	décalage binaire à gauche
&	Binary AND
\|	Binary OR
^	Exclusive binary OR

LAB #9

trainee@debian8:~/training$ x=2
trainee@debian8:~/training$ ((x=$x+10))
trainee@debian8:~/training$ echo $x
12
trainee@debian8:~/training$ ((x=$x+20))
trainee@debian8:~/training$ echo $x
32

trainee@ubuntu1604:~/training$ x=2
trainee@ubuntu1604:~/training$ ((x=$x+10))
trainee@ubuntu1604:~/training$ echo $x
12
trainee@ubuntu1604:~/training$ ((x=$x+20))
trainee@ubuntu1604:~/training$ echo $x
32

[trainee@centos7 training]$ x=2
[trainee@centos7 training]$ ((x=$x+10))
[trainee@centos7 training]$ echo $x
12
[trainee@centos7 training]$ ((x=$x+20))
[trainee@centos7 training]$ echo $x
32

trainee@SLES12SP1:~/training> x=2
trainee@SLES12SP1:~/training> ((x=$x+10))
trainee@SLES12SP1:~/training> echo $x
12
trainee@SLES12SP1:~/training> ((x=$x+20))
trainee@SLES12SP1:~/training> echo $x
32

Control Structures

If

The syntax is as follows:

if condition
then
    command(s)
else 
    command(s)
fi

or:

if condition
then
    command(s)
    command(s)
fi

or finally:

if condition
then
     command(s)
elif condition
then
     command(s)
elif condition
then
     command(s)
else 
    command(s)

fi

case

The syntax is as follows:

case $variable in
model1) function
   ...
   ;;
model2) function
   ...
   ;;
model3 | model4 | model5 ) function
   ...
   ;;
esac

Loops

for

The syntax is as follows:

for variable in variable_list
do
    command(s)
done

while

The syntax is as follows:

while condition
do
    command(s)
done

Example

U=1
while [ $U -lt $MAX_ACCOUNTS ]
do
useradd fenestros"$U" -c fenestros"$U" -d /home/fenestros"$U" -g staff -G audio,fuse -s /bin/bash 2>/dev/null
useradd fenestros"$U"$ -g machines -s /dev/false -d /dev/null 2>/dev/null
echo "Compte fenestros$U créé"
let U=U+1
done

Start-up Scripts

When Bash is called as a login shell it executes the start-up scripts in the following order:

/etc/profile,
~/.bash_profile or ~/.bash_login or ~/.profile dependant upon the distribution,

In the case of RHEL/CentOS, Bash executes ~/.bash_profile. In the cas of Debian, Ubuntu and SLES, Bash executes ~/.profile.

When a login shell is terminated, Bash executes the ~/.bash_logout file if it exists.

Whan Bash is called as an interactive shell as opposed to a login shell, it executes only the ~/.bashrc file.

LAB #11

To do : Using the knowledge you have acquired in this unit, explain each of the following scripts.

~/.profile and ~/.bash_profile

trainee@debian8:~/training$ cat ~/.profile
# ~/.profile: executed by the command interpreter for login shells.
# This file is not read by bash(1), if ~/.bash_profile or ~/.bash_login
# exists.
# see /usr/share/doc/bash/examples/startup-files for examples.
# the files are located in the bash-doc package.

# the default umask is set in /etc/profile; for setting the umask
# for ssh logins, install and configure the libpam-umask package.
#umask 022

# if running bash
if [ -n "$BASH_VERSION" ]; then
    # include .bashrc if it exists
    if [ -f "$HOME/.bashrc" ]; then
	. "$HOME/.bashrc"
    fi
fi

# set PATH so it includes user's private bin if it exists
if [ -d "$HOME/bin" ] ; then
    PATH="$HOME/bin:$PATH"
fi

trainee@ubuntu1604:~/training$ cat ~/.profile
# ~/.profile: executed by the command interpreter for login shells.
# This file is not read by bash(1), if ~/.bash_profile or ~/.bash_login
# exists.
# see /usr/share/doc/bash/examples/startup-files for examples.
# the files are located in the bash-doc package.

# the default umask is set in /etc/profile; for setting the umask
# for ssh logins, install and configure the libpam-umask package.
#umask 022

# if running bash
if [ -n "$BASH_VERSION" ]; then
    # include .bashrc if it exists
    if [ -f "$HOME/.bashrc" ]; then
	. "$HOME/.bashrc"
    fi
fi

# set PATH so it includes user's private bin if it exists
if [ -d "$HOME/bin" ] ; then
    PATH="$HOME/bin:$PATH"
fi

[trainee@centos7 training]$ cat ~/.bash_profile
# .bash_profile

# Get the aliases and functions
if [ -f ~/.bashrc ]; then
	. ~/.bashrc
fi

# User specific environment and startup programs

PATH=$PATH:$HOME/.local/bin:$HOME/bin

export PATH

trainee@SLES12SP1:~/training> cat ~/.profile
# Sample .profile for SuSE Linux
# rewritten by Christian Steinruecken <cstein@suse.de>
#
# This file is read each time a login shell is started.
# All other interactive shells will only read .bashrc; this is particularly
# important for language settings, see below.

test -z "$PROFILEREAD" && . /etc/profile || true

# Most applications support several languages for their output.
# To make use of this feature, simply uncomment one of the lines below or
# add your own one (see /usr/share/locale/locale.alias for more codes)
# This overwrites the system default set in /etc/sysconfig/language
# in the variable RC_LANG.
#
#export LANG=de_DE.UTF-8	# uncomment this line for German output
#export LANG=fr_FR.UTF-8	# uncomment this line for French output
#export LANG=es_ES.UTF-8	# uncomment this line for Spanish output


# Some people don't like fortune. If you uncomment the following lines,
# you will have a fortune each time you log in ;-)

#if [ -x /usr/bin/fortune ] ; then
#    echo
#    /usr/bin/fortune
#    echo
#fi

~/.bashrc

trainee@debian8:~/training$ cat ~/.bashrc
# ~/.bashrc: executed by bash(1) for non-login shells.
# see /usr/share/doc/bash/examples/startup-files (in the package bash-doc)
# for examples

# If not running interactively, don't do anything
case $- in
    *i*) ;;
      *) return;;
esac

# don't put duplicate lines or lines starting with space in the history.
# See bash(1) for more options
HISTCONTROL=ignoreboth

# append to the history file, don't overwrite it
shopt -s histappend

# for setting history length see HISTSIZE and HISTFILESIZE in bash(1)
HISTSIZE=1000
HISTFILESIZE=2000

# check the window size after each command and, if necessary,
# update the values of LINES and COLUMNS.
shopt -s checkwinsize

# If set, the pattern "**" used in a pathname expansion context will
# match all files and zero or more directories and subdirectories.
#shopt -s globstar

# make less more friendly for non-text input files, see lesspipe(1)
#[ -x /usr/bin/lesspipe ] && eval "$(SHELL=/bin/sh lesspipe)"

# set variable identifying the chroot you work in (used in the prompt below)
if [ -z "${debian_chroot:-}" ] && [ -r /etc/debian_chroot ]; then
    debian_chroot=$(cat /etc/debian_chroot)
fi

# set a fancy prompt (non-color, unless we know we "want" color)
case "$TERM" in
    xterm-color) color_prompt=yes;;
esac

# uncomment for a colored prompt, if the terminal has the capability; turned
# off by default to not distract the user: the focus in a terminal window
# should be on the output of commands, not on the prompt
#force_color_prompt=yes

if [ -n "$force_color_prompt" ]; then
    if [ -x /usr/bin/tput ] && tput setaf 1 >&/dev/null; then
	# We have color support; assume it's compliant with Ecma-48
	# (ISO/IEC-6429). (Lack of such support is extremely rare, and such
	# a case would tend to support setf rather than setaf.)
	color_prompt=yes
    else
	color_prompt=
    fi
fi

if [ "$color_prompt" = yes ]; then
    PS1='${debian_chroot:+($debian_chroot)}\[\033[01;32m\]\u@\h\[\033[00m\]:\[\033[01;34m\]\w\[\033[00m\]\$ '
else
    PS1='${debian_chroot:+($debian_chroot)}\u@\h:\w\$ '
fi
unset color_prompt force_color_prompt

# If this is an xterm set the title to user@host:dir
case "$TERM" in
xterm*|rxvt*)
    PS1="\[\e]0;${debian_chroot:+($debian_chroot)}\u@\h: \w\a\]$PS1"
    ;;
*)
    ;;
esac

# enable color support of ls and also add handy aliases
if [ -x /usr/bin/dircolors ]; then
    test -r ~/.dircolors && eval "$(dircolors -b ~/.dircolors)" || eval "$(dircolors -b)"
    alias ls='ls --color=auto'
    #alias dir='dir --color=auto'
    #alias vdir='vdir --color=auto'

    #alias grep='grep --color=auto'
    #alias fgrep='fgrep --color=auto'
    #alias egrep='egrep --color=auto'
fi

# colored GCC warnings and errors
#export GCC_COLORS='error=01;31:warning=01;35:note=01;36:caret=01;32:locus=01:quote=01'

# some more ls aliases
#alias ll='ls -l'
#alias la='ls -A'
#alias l='ls -CF'

# Alias definitions.
# You may want to put all your additions into a separate file like
# ~/.bash_aliases, instead of adding them here directly.
# See /usr/share/doc/bash-doc/examples in the bash-doc package.

if [ -f ~/.bash_aliases ]; then
    . ~/.bash_aliases
fi

# enable programmable completion features (you don't need to enable
# this, if it's already enabled in /etc/bash.bashrc and /etc/profile
# sources /etc/bash.bashrc).
if ! shopt -oq posix; then
  if [ -f /usr/share/bash-completion/bash_completion ]; then
    . /usr/share/bash-completion/bash_completion
  elif [ -f /etc/bash_completion ]; then
    . /etc/bash_completion
  fi
fi

trainee@ubuntu1604:~/training$ cat ~/.bashrc
# ~/.bashrc: executed by bash(1) for non-login shells.
# see /usr/share/doc/bash/examples/startup-files (in the package bash-doc)
# for examples

# If not running interactively, don't do anything
case $- in
    *i*) ;;
      *) return;;
esac

# don't put duplicate lines or lines starting with space in the history.
# See bash(1) for more options
HISTCONTROL=ignoreboth

# append to the history file, don't overwrite it
shopt -s histappend

# for setting history length see HISTSIZE and HISTFILESIZE in bash(1)
HISTSIZE=1000
HISTFILESIZE=2000

# check the window size after each command and, if necessary,
# update the values of LINES and COLUMNS.
shopt -s checkwinsize

# If set, the pattern "**" used in a pathname expansion context will
# match all files and zero or more directories and subdirectories.
#shopt -s globstar

# make less more friendly for non-text input files, see lesspipe(1)
[ -x /usr/bin/lesspipe ] && eval "$(SHELL=/bin/sh lesspipe)"

# set variable identifying the chroot you work in (used in the prompt below)
if [ -z "${debian_chroot:-}" ] && [ -r /etc/debian_chroot ]; then
    debian_chroot=$(cat /etc/debian_chroot)
fi

# set a fancy prompt (non-color, unless we know we "want" color)
case "$TERM" in
    xterm-color|*-256color) color_prompt=yes;;
esac

# uncomment for a colored prompt, if the terminal has the capability; turned
# off by default to not distract the user: the focus in a terminal window
# should be on the output of commands, not on the prompt
#force_color_prompt=yes

if [ -n "$force_color_prompt" ]; then
    if [ -x /usr/bin/tput ] && tput setaf 1 >&/dev/null; then
	# We have color support; assume it's compliant with Ecma-48
	# (ISO/IEC-6429). (Lack of such support is extremely rare, and such
	# a case would tend to support setf rather than setaf.)
	color_prompt=yes
    else
	color_prompt=
    fi
fi

if [ "$color_prompt" = yes ]; then
    PS1='${debian_chroot:+($debian_chroot)}\[\033[01;32m\]\u@\h\[\033[00m\]:\[\033[01;34m\]\w\[\033[00m\]\$ '
else
    PS1='${debian_chroot:+($debian_chroot)}\u@\h:\w\$ '
fi
unset color_prompt force_color_prompt

# If this is an xterm set the title to user@host:dir
case "$TERM" in
xterm*|rxvt*)
    PS1="\[\e]0;${debian_chroot:+($debian_chroot)}\u@\h: \w\a\]$PS1"
    ;;
*)
    ;;
esac

# enable color support of ls and also add handy aliases
if [ -x /usr/bin/dircolors ]; then
    test -r ~/.dircolors && eval "$(dircolors -b ~/.dircolors)" || eval "$(dircolors -b)"
    alias ls='ls --color=auto'
    #alias dir='dir --color=auto'
    #alias vdir='vdir --color=auto'

    alias grep='grep --color=auto'
    alias fgrep='fgrep --color=auto'
    alias egrep='egrep --color=auto'
fi

# colored GCC warnings and errors
#export GCC_COLORS='error=01;31:warning=01;35:note=01;36:caret=01;32:locus=01:quote=01'

# some more ls aliases
alias ll='ls -alF'
alias la='ls -A'
alias l='ls -CF'

# Add an "alert" alias for long running commands.  Use like so:
#   sleep 10; alert
alias alert='notify-send --urgency=low -i "$([ $? = 0 ] && echo terminal || echo error)" "$(history|tail -n1|sed -e '\''s/^\s*[0-9]\+\s*//;s/[;&|]\s*alert$//'\'')"'

# Alias definitions.
# You may want to put all your additions into a separate file like
# ~/.bash_aliases, instead of adding them here directly.
# See /usr/share/doc/bash-doc/examples in the bash-doc package.

if [ -f ~/.bash_aliases ]; then
    . ~/.bash_aliases
fi

# enable programmable completion features (you don't need to enable
# this, if it's already enabled in /etc/bash.bashrc and /etc/profile
# sources /etc/bash.bashrc).
if ! shopt -oq posix; then
  if [ -f /usr/share/bash-completion/bash_completion ]; then
    . /usr/share/bash-completion/bash_completion
  elif [ -f /etc/bash_completion ]; then
    . /etc/bash_completion
  fi
fi

[trainee@centos7 training]$ cat ~/.bashrc
# .bashrc

# Source global definitions
if [ -f /etc/bashrc ]; then
	. /etc/bashrc
fi

# Uncomment the following line if you don't like systemctl's auto-paging feature:
# export SYSTEMD_PAGER=

# User specific aliases and functions

trainee@SLES12SP1:~/training> cat ~/.bashrc
# Sample .bashrc for SuSE Linux
# Copyright (c) SuSE GmbH Nuernberg

# There are 3 different types of shells in bash: the login shell, normal shell
# and interactive shell. Login shells read ~/.profile and interactive shells
# read ~/.bashrc; in our setup, /etc/profile sources ~/.bashrc - thus all
# settings made here will also take effect in a login shell.
#
# NOTE: It is recommended to make language settings in ~/.profile rather than
# here, since multilingual X sessions would not work properly if LANG is over-
# ridden in every subshell.

# Some applications read the EDITOR variable to determine your favourite text
# editor. So uncomment the line below and enter the editor of your choice :-)
#export EDITOR=/usr/bin/vim
#export EDITOR=/usr/bin/mcedit

# For some news readers it makes sense to specify the NEWSSERVER variable here
#export NEWSSERVER=your.news.server

# If you want to use a Palm device with Linux, uncomment the two lines below.
# For some (older) Palm Pilots, you might need to set a lower baud rate
# e.g. 57600 or 38400; lowest is 9600 (very slow!)
#
#export PILOTPORT=/dev/pilot
#export PILOTRATE=115200

test -s ~/.alias && . ~/.alias || true

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Copyright © 2004-2017 Hugh Norris.<br><br> <a rel=“license” href=“http://creativecommons.org/licenses/by-nc-nd/3.0/fr/”><img alt=“Licence Creative Commons” style=“border-width:0” src=“http://i.creativecommons.org/l/by-nc-nd/3.0/fr/88x31.png” /></a><br />Ce(tte) oeuvre est mise à disposition selon les termes de la <a rel=“license” href=“http://creativecommons.org/licenses/by-nc-nd/3.0/fr/”>Licence Creative Commons Attribution - Pas d’Utilisation Commerciale - Pas de Modification 3.0 France</a>.

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