Each manual page has a short description available within it.
apropos
searches the descriptions for instances of
keyword.
keyword
is usually a regular expression, as if
(-r)
was used, or
may contain wildcards
(-w) ,
or match the exact keyword
(-e) .
Using these options, it may be necessary to quote the
keyword
or escape (\) the special characters to stop the shell from interpreting
them.
The standard matching rules allow matches to be made against the page name
and word boundaries in the description.
OPTIONS
-d, --debug
Print debugging information.
-r, --regex
Interpret each keyword as a regular expression.
This is the default behaviour.
Each keyword will be matched against the page names and the descriptions
independently.
It can match any part of either.
The match is not limited to word boundaries.
-w, --wildcard
Interpret each keyword as a pattern containing shell style wildcards.
Each keyword will be matched against the page names and the descriptions
independently.
A match will only be found if an expanded keyword matches an entire
description or page name.
-e, --exact
Each keyword will be exactly matched against the page names and the
descriptions.
-m system [,...],--systems=system[,...]
If this system has access to other operating system's manual page
descriptions, they can be searched using this option.
To search NewOS's manual page descriptions, use the option
-mNewOS.
The
system
specified can be a combination of comma-delimited operating system names.
To include a search of the native operating system's
whatis
descriptions, include the system name
man
in the argument string.
This option will override the
$SYSTEM
environment variable.
-M path, --manpath=path
Specify an alternate set of colon-delimited manual page hierarchies to
search.
By default,
apropos
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.
-h, --help
Print a help message and exit.
-V, --version
Display version and author 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.
POSIXLY_CORRECT
If
$POSIXLY_CORRECT
is set, even to a null value, the default
apropos
search will be as an extended regex
(-r) .
Nowadays, this is the default behaviour anyway.
FILES
/usr/share/man/index.(bt|db|dir|pag)
A traditional global
index
database cache.
/var/cache/man/index.(bt|db|dir|pag)
An alternate or FHS
compliant global
index
database cache.