The whatis command is a Linux command that can be used to get a brief description of a command. It is a versatile command that can be used to quickly get a summary of a command's purpose and usage.
The whatis command is used as follows:
whatis command
command: This is the name of the command that you want to get a description of.
For example, the following command will get a brief description of the wc command:
whatis wc
The output of the whatis command will be:
wc (1) - count lines, words, and characters
This output shows that the wc command is used to count the lines, words, and characters in a file.
The whatis command can be used to get a brief description of any command. It is a valuable tool for system administrators who need to learn about the commands that are available on their system. It can also be used by users to get a quick summary of a command's purpose and usage.
Here are some other examples of how the whatis command can be used:
To get a description of the ls command:
whatis ls
To get a description of the grep command:
whatis grep
To get a description of the man command:
whatis man
The whatis command is a quick and easy way to get a brief description of a command. It is a valuable tool for anyone who needs to learn about the commands that are available on their system.
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.
man
NAME
whatis - display one-line manual page descriptions
SYNOPSIS
whatis [-dlv?V] [-r|-w] [-s list] [-m system[,...]] [-M path] [-L locale] [-C file] name ...
DESCRIPTION
Each manual page has a short description available within it. whatis searches the manual page names and displays the manual
page descriptions of any name matched.
name may contain wildcards (-w) or be a regular expression (-r). Using these options, it may be necessary to quote the name
or escape (\) the special characters to stop the shell from interpreting them.
index databases are used during the search, and are updated by the mandb program. Depending on your installation, this may
be run by a periodic cron job, or may need to be run manually after new manual pages have been installed. To produce an old
style text whatis database from the relative index database, issue the command:
whatis -M manpath -w '*' | sort > manpath/whatis
where manpath is a manual page hierarchy such as /usr/man.
OPTIONS
-d, --debug
Print debugging information.
-v, --verbose
Print verbose warning messages.
-r, --regex
Interpret each name as a regular expression. If a name matches any part of a page name, a match will be made. This
option causes whatis to be somewhat slower due to the nature of database searches.
-w, --wildcard
Interpret each name as a pattern containing shell style wildcards. For a match to be made, an expanded name must
match the entire page name. This option causes whatis to be somewhat slower due to the nature of database searches.
-l, --long
Do not trim output to the terminal width. Normally, output will be truncated to the terminal width to avoid ugly re‐
sults from poorly-written NAME sections.
-s list, --sections=list, --section=list
Search only the given manual sections. list is a colon- or comma-separated list of sections. If an entry in list is
a simple section, for example "3", then the displayed list of descriptions will include pages in sections "3",
"3perl", "3x", and so on; while if an entry in list has an extension, for example "3perl", then the list will only in‐
clude pages in that exact part of the manual section.
-m system[,...], --systems=system[,...]
If this system has access to other operating systems' manual page names, they can be accessed using this option. To
search NewOS's manual page names, use the option -m NewOS.
The system specified can be a combination of comma delimited operating system names. To include a search of the na‐
tive operating system's manual page names, include the system name man in the argument string. This option will over‐
ride the $SYSTEM environment variable.
-M path, --manpath=path
Specify an alternate set of colon-delimited manual page hierarchies to search. By default, whatis uses the $MANPATH
environment variable, unless it is empty or unset, in which case it will determine an appropriate manpath based on
your $PATH environment variable. This option overrides the contents of $MANPATH.
-L locale, --locale=locale
whatis will normally determine your current locale by a call to the C function setlocale(3) which interrogates various
environment variables, possibly including $LC_MESSAGES and $LANG. To temporarily override the determined value, use
this option to supply a locale string directly to whatis. Note that it will not take effect until the search for
pages actually begins. Output such as the help message will always be displayed in the initially determined locale.
-C file, --config-file=file
Use this user configuration file rather than the default of ~/.manpath.
-?, --help
Print a help message and exit.
--usage
Print a short usage message and exit.
-V, --version
Display version information.
EXIT STATUS
0 Successful program execution.
1 Usage, syntax or configuration file error.
2 Operational error.
16 Nothing was found that matched the criteria specified.
ENVIRONMENT
SYSTEM If $SYSTEM is set, it will have the same effect as if it had been specified as the argument to the -m option.
MANPATH
If $MANPATH is set, its value is interpreted as the colon-delimited manual page hierarchy search path to use.
See the SEARCH PATH section of manpath(5) for the default behaviour and details of how this environment variable is
handled.
MANWIDTH
If $MANWIDTH is set, its value is used as the terminal width (see the --long option). If it is not set, the terminal
width will be calculated using the value of $COLUMNS, and ioctl(2) if available, or falling back to 80 characters if
all else fails.
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