Table des matières
Last updated on: 2020/01/30 03:28
Help and Documentation
Help on external commands
External commands are binary executables or scripts generally found in /bin, /sbin, /usr/bin ou /usr/sbin :
[root@centos7 ~]# type ifconfig ifconfig is /sbin/ifconfig
Help for an external command can generally be obtained by using the –help option with the command in question :
[root@centos7 ~]# du --help | more
Usage: du [OPTION]... [FILE]...
or: du [OPTION]... --files0-from=F
Summarize disk usage of each FILE, recursively for directories.
Mandatory arguments to long options are mandatory for short options too.
-0, --null end each output line with 0 byte rather than newline
-a, --all write counts for all files, not just directories
--apparent-size print apparent sizes, rather than disk usage; although
the apparent size is usually smaller, it may be
larger due to holes in ('sparse') files, internal
fragmentation, indirect blocks, and the like
-B, --block-size=SIZE scale sizes by SIZE before printing them; e.g.,
'-BM' prints sizes in units of 1,048,576 bytes;
see SIZE format below
-b, --bytes equivalent to '--apparent-size --block-size=1'
-c, --total produce a grand total
-D, --dereference-args dereference only symlinks that are listed on the
command line
-d, --max-depth=N print the total for a directory (or file, with --all)
only if it is N or fewer levels below the command
line argument; --max-depth=0 is the same as
--summarize
--files0-from=F summarize disk usage of the
--More--
Use with certain commands, the –help option is not valid:
[root@centos7 ~]# type --help -bash: type: --: invalid option type: usage: type [-afptP] name [name ...]
Help on built-in commands
Commands such as type, cd or umask are internal to the shell:
[root@centos7 ~]# type type type is a shell builtin
One of the internal Bash commands is help. Used with no argument, this command shows a list of all the internal commands:
[root@centos7 ~]# help | more GNU bash, version 4.2.46(1)-release (x86_64-redhat-linux-gnu) These shell commands are defined internally. Type `help' to see this list. Type `help name' to find out more about the function `name'. Use `info bash' to find out more about the shell in general. Use `man -k' or `info' to find out more about commands not in this list. A star (*) next to a name means that the command is disabled. job_spec [&] history [-c] [-d offset] [n] or history -anr> (( expression )) if COMMANDS; then COMMANDS; [ elif COMMANDS;> . filename [arguments] jobs [-lnprs] [jobspec ...] or jobs -x comma> : kill [-s sigspec | -n signum | -sigspec] pid> [ arg... ] let arg [arg ...] [[ expression ]] local [option] name[=value] ... alias [-p] [name[=value] ... ] logout [n] bg [job_spec ...] mapfile [-n count] [-O origin] [-s count] [-> bind [-lpvsPVS] [-m keymap] [-f filename] [-q> popd [-n] [+N | -N] break [n] printf [-v var] format [arguments] builtin [shell-builtin [arg ...]] pushd [-n] [+N | -N | dir] caller [expr] pwd [-LP] case WORD in [PATTERN [| PATTERN]...) COMMAND> read [-ers] [-a array] [-d delim] [-i text] > cd [-L|[-P [-e]]] [dir] readarray [-n count] [-O origin] [-s count] > command [-pVv] command [arg ...] readonly [-aAf] [name[=value] ...] or readon> --More--
To get help concerning a given internal command, help is invoked with the given command as an argument:
[root@centos7 ~]# help type
type: type [-afptP] name [name ...]
Display information about command type.
For each NAME, indicate how it would be interpreted if used as a
command name.
Options:
-a display all locations containing an executable named NAME;
includes aliases, builtins, and functions, if and only if
the `-p' option is not also used
-f suppress shell function lookup
-P force a PATH search for each NAME, even if it is an alias,
builtin, or function, and returns the name of the disk file
that would be executed
-p returns either the name of the disk file that would be executed,
or nothing if `type -t NAME' would not return `file'.
-t output a single word which is one of `alias', `keyword',
`function', `builtin', `file' or `', if NAME is an alias, shell
reserved word, shell function, shell builtin, disk file, or not
found, respectively
Arguments:
NAME Command name to be interpreted.
Exit Status:
Returns success if all of the NAMEs are found; fails if any are not found.
typeset: typeset [-aAfFgilrtux] [-p] name[=value] ...
Set variable values and attributes.
Obsolete. See `help declare'.
The man command
The man command is used to consult the manual of the command passed as an argument, for example man help:
BASH_BUILTINS(1) General Commands Manual BASH_BUILTINS(1)
NAME
bash, :, ., [, alias, bg, bind, break, builtin, caller, cd, command, compgen, com‐
plete, compopt, continue, declare, dirs, disown, echo, enable, eval, exec, exit,
export, false, fc, fg, getopts, hash, help, history, jobs, kill, let, local, logout,
mapfile, popd, printf, pushd, pwd, read, readonly, return, set, shift, shopt, source,
suspend, test, times, trap, true, type, typeset, ulimit, umask, unalias, unset, wait -
bash built-in commands, see bash(1)
BASH BUILTIN COMMANDS
Unless otherwise noted, each builtin command documented in this section as accepting
options preceded by - accepts -- to signify the end of the options. The :, true,
false, and test builtins do not accept options and do not treat -- specially. The
exit, logout, break, continue, let, and shift builtins accept and process arguments
beginning with - without requiring --. Other builtins that accept arguments but are
not specified as accepting options interpret arguments beginning with - as invalid
options and require -- to prevent this interpretation.
: [arguments]
No effect; the command does nothing beyond expanding arguments and performing
any specified redirections. A zero exit code is returned.
. filename [arguments]
Manual page help(1) line 1 (press h for help or q to quit)
Each manual page can contain several sections:
| Section | Contents |
|---|---|
| NAME | This section is required and has a standardized format consisting of a comma-separated list of program or function names, followed by a dash, followed by a short description of the functionality the program (or function, or file) is supposed to provide. By using the makewhatis command, the name sections are inputted into the whatis database files. |
| SYNOPSIS | This section gives a short overview on available program options. For functions this section lists corresponding include files and the prototype so the programmer knows the type and number of arguments as well as the return type. |
| DESCRIPTION | This section describes how to use the command or function and what each argument does. |
| OPTIONS | This section gives a description of how each option affects program behaviour. |
| FILES | This section lists files the program or function uses. |
| EXAMPLE | This section gives examples of how to use the command or function. |
| ENVIRONMENT | This section lists all environment variables that affect the program or function and explains how they do so. |
| CONFORMING TO | This section lists the eventual standards that the command or function conforms to. |
| BUGS / TO DO | This section describes the limitations and known inconveniences of the command or function. |
| EXIT STATUS / RETURN VALUE | This section lists the exit status codes and their meaning. |
| SEE ALSO | This section provides a list of related man pages in alphabetical order. |
Navigation within a manual is accomplished using the following keys:
| Key | Function |
|---|---|
| Space Bar | Move forward one screen |
| ↵ Enter | Move down one line |
| ↑ | Move up one line |
| ↓ | Move down one line |
| Page↑ | Move up (backwards) one half screen |
| Page↓ | Move down (forward) one half screen |
| Home | Move to the beginning of the manual |
| End | Move to the end of the manual |
| / | Search for the string that follows the / key. The n key then searches for the next occurrence whilst the N searches for the previous occurrence |
| Q | Quit the manual |
A complete Linux manual is comprised of up to 9 sections:
| Section | Contents |
|---|---|
| 1 | Executable programs or shell commands |
| 2 | System calls (functions provided by the kernel) |
| 3 | Library calls (functions within program libraries) |
| 4 | Special files (usually found in /dev) |
| 5 | File formats and conventions eg /etc/passwd |
| 6 | Games |
| 7 | Miscellaneous (including macro packages and conventions), e.g. man(7), groff(7) |
| 8 | System administration commands (usually only for root) |
| 9 | Kernel routines [Non standard] |
The available section for a specific command are given by the output of the whereis command:
[root@centos7 ~]# whereis passwd passwd: /usr/bin/passwd /etc/passwd /usr/share/man/man1/passwd.1.gz /usr/share/man/man5/passwd.5.gz
To consult a specific section of a manual, the section number must be supplied as an argument to the man command:
$ man 5 passwd [Enter]
The -k option of the man command searches for the string supplied as an argument within the list of available manuals:
[root@centos7 ~]# man -k passwd chpasswd (8) - update passwords in batch mode fgetpwent_r (3) - get passwd file entry reentrantly getpwent_r (3) - get passwd file entry reentrantly gpasswd (1) - administer /etc/group and /etc/gshadow grub2-mkpasswd-pbkdf2 (1) - Generate a PBKDF2 password hash. kpasswd (1) - change a user's Kerberos password lpasswd (1) - Change group or user password lppasswd (1) - add, change, or delete digest passwords. pam_localuser (8) - require users to be listed in /etc/passwd passwd (1) - update user's authentication tokens sslpasswd (1ssl) - compute password hashes passwd (5) - password file passwd2des (3) - RFS password encryption pwhistory_helper (8) - Helper binary that transfers password hashes from passwd or shadow to ... smbpasswd (5) - The Samba encrypted password file smbpasswd (8) - change a user's SMB password userpasswd (1) - A graphical tool to allow users to change their passwords. vncpasswd (1) - change the VNC password
The output is a list of the available manuals complete with their description. The number between parentheses indicates the manual section number.
Command Line Switches
The switches associated with the man command are:
[root@centos7 ~]# man --help
Usage: man [OPTION...] [SECTION] PAGE...
-C, --config-file=FILE use this user configuration file
-d, --debug emit debugging messages
-D, --default reset all options to their default values
--warnings[=WARNINGS] enable warnings from groff
Main modes of operation:
-f, --whatis equivalent to whatis
-k, --apropos equivalent to apropos
-K, --global-apropos search for text in all pages
-l, --local-file interpret PAGE argument(s) as local filename(s)
-w, --where, --path, --location
print physical location of man page(s)
-W, --where-cat, --location-cat
print physical location of cat file(s)
-c, --catman used by catman to reformat out of date cat pages
-R, --recode=ENCODING output source page encoded in ENCODING
Finding manual pages:
-L, --locale=LOCALE define the locale for this particular man search
-m, --systems=SYSTEM use manual pages from other systems
-M, --manpath=PATH set search path for manual pages to PATH
-S, -s, --sections=LIST use colon separated section list
-e, --extension=EXTENSION limit search to extension type EXTENSION
-i, --ignore-case look for pages case-insensitively (default)
-I, --match-case look for pages case-sensitively
--regex show all pages matching regex
--wildcard show all pages matching wildcard
--names-only make --regex and --wildcard match page names only,
not descriptions
-a, --all find all matching manual pages
-u, --update force a cache consistency check
--no-subpages don't try subpages, e.g. 'man foo bar' => 'man
foo-bar'
Controlling formatted output:
-P, --pager=PAGER use program PAGER to display output
-r, --prompt=STRING provide the `less' pager with a prompt
-7, --ascii display ASCII translation of certain latin1 chars
-E, --encoding=ENCODING use selected output encoding
--no-hyphenation, --nh turn off hyphenation
--no-justification, --nj turn off justification
-p, --preprocessor=STRING STRING indicates which preprocessors to run:
e - [n]eqn, p - pic, t - tbl,
g - grap, r - refer, v - vgrind
-t, --troff use groff to format pages
-T, --troff-device[=DEVICE] use groff with selected device
-H, --html[=BROWSER] use elinks or BROWSER to display HTML output
-X, --gxditview[=RESOLUTION] use groff and display through gxditview
(X11):
-X = -TX75, -X100 = -TX100, -X100-12 = -TX100-12
-Z, --ditroff use groff and force it to produce ditroff
-?, --help give this help list
--usage give a short usage message
-V, --version print program version
Mandatory or optional arguments to long options are also mandatory or optional
for any corresponding short options.
Report bugs to cjwatson@debian.org.
The apropos command
apropos searches the whatis database for instances of a keyword passed to the command as an argument. With no further options, the output is identical to man -k:
[root@centos7 ~]# apropos passwd chpasswd (8) - update passwords in batch mode fgetpwent_r (3) - get passwd file entry reentrantly getpwent_r (3) - get passwd file entry reentrantly gpasswd (1) - administer /etc/group and /etc/gshadow grub2-mkpasswd-pbkdf2 (1) - Generate a PBKDF2 password hash. kpasswd (1) - change a user's Kerberos password lpasswd (1) - Change group or user password lppasswd (1) - add, change, or delete digest passwords. pam_localuser (8) - require users to be listed in /etc/passwd passwd (1) - update user's authentication tokens sslpasswd (1ssl) - compute password hashes passwd (5) - password file passwd2des (3) - RFS password encryption pwhistory_helper (8) - Helper binary that transfers password hashes from passwd or shadow to ... smbpasswd (5) - The Samba encrypted password file smbpasswd (8) - change a user's SMB password userpasswd (1) - A graphical tool to allow users to change their passwords. vncpasswd (1) - change the VNC password
Command Line Switches
The switches associated with the apropos command are:
[root@centos7 ~]# apropos --help
Usage: apropos [OPTION...] KEYWORD...
-d, --debug emit debugging messages
-v, --verbose print verbose warning messages
-e, --exact search each keyword for exact match
-r, --regex interpret each keyword as a regex
-w, --wildcard the keyword(s) contain wildcards
-a, --and require all keywords to match
-l, --long do not trim output to terminal width
-C, --config-file=FILE use this user configuration file
-L, --locale=LOCALE define the locale for this search
-m, --systems=SYSTEM use manual pages from other systems
-M, --manpath=PATH set search path for manual pages to PATH
-s, --sections=LIST, --section=LIST
search only these sections (colon-separated)
-?, --help give this help list
--usage give a short usage message
-V, --version print program version
Mandatory or optional arguments to long options are also mandatory or optional
for any corresponding short options.
The --regex option is enabled by default.
Report bugs to cjwatson@debian.org.
The makewhatis and whatis Commands under RHEL/CentOS 6
Each manual page has a short description available within it. These descriptions as well as the name of the manual are stored in the whatis database. The whatis database is created by /usr/sbin/makewhatis.
The use of makewhatis is extremely simple:
[root@centos6 ~]# makewhatis
The whatis command can now be used to identify the man sections available for the passwd command:
[root@centos6 ~]# whatis passwd passwd (1) - update user's authentication tokens passwd (5) - password file passwd [sslpasswd] (1ssl) - compute password hashes
Command Line Switches
The switches associated with the makewhatis command are:
[root@centos6 ~]# makewhatis --help
Usage: makewhatis [-s sections] [-u] [-v] [-w] [manpath] [-c [catpath]] [-o whatisdb]
This will build the whatis database for the man pages
found in manpath and the cat pages found in catpath.
-s: sections (default: 1 1p 8 2 3 3p 4 5 6 7 9 0p n l p o 1x 2x 3x 4x 5x 6x 7x 8x)
-u: update database with pages added today
-U: update database with pages added since last makewhatis run
-v: verbose
-o: location of whatis database (default: /var/cache/man/whatis)
-w: use manpath obtained from `man --path`
[manpath]: man directories (default: /usr/share/man)
[catpath]: cat directories (default: the first existing
directory in /usr/share/man)
The switches associated with the whatis command are:
Usage: whatis [OPTION...] KEYWORD...
-d, --debug emit debugging messages
-v, --verbose print verbose warning messages
-r, --regex interpret each keyword as a regex
-w, --wildcard the keyword(s) contain wildcards
-l, --long do not trim output to terminal width
-C, --config-file=FILE use this user configuration file
-L, --locale=LOCALE define the locale for this search
-m, --systems=SYSTEM use manual pages from other systems
-M, --manpath=PATH set search path for manual pages to PATH
-s, --section=SECTION search only this section
-?, --help give this help list
--usage give a short usage message
-V, --version print program version
Mandatory or optional arguments to long options are also mandatory or optional
for any corresponding short options.
Report bugs to cjwatson@debian.org.
The mandb and whatis commands with RHEL/CentOS 7
The whatis database is maintained by root by using the /bin/mandb or /usr/bin/mandb command.
The use of mandb is very simple:
[root@centos7 ~]# mandb Purging old database entries in /usr/share/man... mandb: warning: /usr/share/man/man8/fsck.fat.8.manpage-fix.gz: ignoring bogus filename Processing manual pages under /usr/share/man... Purging old database entries in /usr/share/man/ca... Processing manual pages under /usr/share/man/ca... Purging old database entries in /usr/share/man/cs... Processing manual pages under /usr/share/man/cs... Purging old database entries in /usr/share/man/da... Processing manual pages under /usr/share/man/da... Purging old database entries in /usr/share/man/de... Processing manual pages under /usr/share/man/de... Purging old database entries in /usr/share/man/en... ... 0 man subdirectories contained newer manual pages. 0 manual pages were added. 0 stray cats were added. 0 old database entries were purged.
Now the whatis command can be used to check which manual sections are available for a specific command:
[root@centos7 ~]# whatis passwd sslpasswd (1ssl) - compute password hashes passwd (1) - update user's authentication tokens passwd (5) - password file
Command Line Switches
The switches associated with the mandb command are:
[root@centos7 ~]# mandb --help
Usage: mandb [OPTION...] [MANPATH]
-c, --create create dbs from scratch, rather than updating
-C, --config-file=FILE use this user configuration file
-d, --debug emit debugging messages
-f, --filename=FILENAME update just the entry for this filename
-p, --no-purge don't purge obsolete entries from the dbs
-q, --quiet work quietly, except for 'bogus' warning
-s, --no-straycats don't look for or add stray cats to the dbs
-t, --test check manual pages for correctness
-u, --user-db produce user databases only
-?, --help give this help list
--usage give a short usage message
-V, --version print program version
Mandatory or optional arguments to long options are also mandatory or optional
for any corresponding short options.
Report bugs to cjwatson@debian.org.
The switches associated with the whatis command are:
[root@centos7 ~]# whatis --help
Usage: whatis [OPTION...] KEYWORD...
-d, --debug emit debugging messages
-v, --verbose print verbose warning messages
-r, --regex interpret each keyword as a regex
-w, --wildcard the keyword(s) contain wildcards
-l, --long do not trim output to terminal width
-C, --config-file=FILE use this user configuration file
-L, --locale=LOCALE define the locale for this search
-m, --systems=SYSTEM use manual pages from other systems
-M, --manpath=PATH set search path for manual pages to PATH
-s, --sections=LIST, --section=LIST
search only these sections (colon-separated)
-?, --help give this help list
--usage give a short usage message
-V, --version print program version
Mandatory or optional arguments to long options are also mandatory or optional
for any corresponding short options.
Report bugs to cjwatson@debian.org.
The info command
In addition to the man system, information regarding programs and commands can also be found using the info system. Background information, tutorials, and detailed information on using the program in question are sometimes lacking in man pages and as a result the info system was created to resolve that issue.
Within the info system, multiple individual pages of information make up the entire set of info pages for each specific application. These pages of information are referred to as nodes. You can page through nodes one at a time, or you can jump to specific pages through the use of hypertext links.
To help node navigation, info pages all display a header across the top of the page. This header includes information such as the current node, next and previous nodes, and information regarding the parent node. Navigation is accomplished using the following keys :
| Key | Function |
|---|---|
| n | Next node. |
| p | Previous node. |
| u | Parent node. |
| Space | Scroll down one page at a time. |
| Del | Scroll up one page at a time. |
| b | Return to the beginning of the current node. |
| Tab ⇆ | Select next hypertext link. |
| m <link text> | Performs a direct jump to the specified subnode. Pressing Tab displays all available subnodes. |
| ↵ Enter | Follow current hypertext link. Hypertext links are designated by an asterisk * at the beginning of the link, and a colon : at the end of the link. |
| q | Quit the info system. |
To access the top node of the info system, use the following command :
[root@centos7 ~]# info
...
File: dir Node: Top This is the top of the INFO tree
This (the Directory node) gives a menu of major topics.
Typing "q" exits, "?" lists all Info commands, "d" returns here,
"h" gives a primer for first-timers,
"mEmacs<Return>" visits the Emacs topic, etc.
In Emacs, you can click mouse button 2 on a menu item or cross reference
to select it.
* Menu:
Archiving
* Cpio: (cpio). Copy-in-copy-out archiver to tape or disk.
* Tar: (tar). Making tape (or disk) archives.
Basics
* Common options: (coreutils)Common options.
* Coreutils: (coreutils). Core GNU (file, text, shell) utilities.
* Date input formats: (coreutils)Date input formats.
* File permissions: (coreutils)File permissions.
Access modes.
-----Info: (dir)Top, 2027 lines --Top-----------------------------------------------------------
Welcome to Info version 5.1. Type h for help, m for menu item.
Note that the version of the info command differs from one distribution to another:
[root@centos7 ~]# info -O --version info (GNU texinfo) 5.1 Copyright (C) 2013 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html> This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law.
Command Line Switches
The switches associated with the info command are:
[root@centos7 ~]# info --help
Usage: info [OPTION]... [MENU-ITEM...]
Read documentation in Info format.
Options:
-k, --apropos=STRING look up STRING in all indices of all manuals.
-d, --directory=DIR add DIR to INFOPATH.
--dribble=FILENAME remember user keystrokes in FILENAME.
-f, --file=FILENAME specify Info file to visit.
-h, --help display this help and exit.
--index-search=STRING go to node pointed by index entry STRING.
-n, --node=NODENAME specify nodes in first visited Info file.
-o, --output=FILENAME output selected nodes to FILENAME.
-R, --raw-escapes output "raw" ANSI escapes (default).
--no-raw-escapes output escapes as literal text.
--restore=FILENAME read initial keystrokes from FILENAME.
-O, --show-options, --usage go to command-line options node.
--strict-node-location (for debugging) use Info file pointers as-is.
--subnodes recursively output menu items.
--vi-keys use vi-like and less-like key bindings.
--version display version information and exit.
-w, --where, --location print physical location of Info file.
The first non-option argument, if present, is the menu entry to start from;
it is searched for in all `dir' files along INFOPATH.
If it is not present, info merges all `dir' files and shows the result.
Any remaining arguments are treated as the names of menu
items relative to the initial node visited.
For a summary of key bindings, type h within Info.
Examples:
info show top-level dir menu
info info show the general manual for Info readers
info info-stnd show the manual specific to this Info program
info emacs start at emacs node from top-level dir
info emacs buffers start at buffers node within emacs manual
info --show-options emacs start at node with emacs' command line options
info --subnodes -o out.txt emacs dump entire manual to out.txt
info -f ./foo.info show file ./foo.info, not searching dir
Email bug reports to bug-texinfo@gnu.org,
general questions and discussion to help-texinfo@gnu.org.
Texinfo home page: http://www.gnu.org/software/texinfo/
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Copyright © 2004-2019 Hugh Norris.<br><br>
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