Displays a list of all topics in the man pages that are related to the subject of a query.
The apropos command lists the man pages in which the occurrence of at least one of its arguments can be found in the NAME secion or the SYNOPSIS section.
On most systems apropos is implemented by:
alias apropos="man -k"
By default each argument is searched independently, unless -a is given. For example:
$ apropos ulimit -a get
ulimit (3) - get and set user limits
ulimit (3p) - get and set process limits
$ apropos ulimit get
ulimit (1p) - set or report file size limit
getmsg (2) - unimplemented system calls
ulimit (3) - get and set user limits
ulimit (3p) - get and set process limits
ulimit.h (0p) - ulimit commands
zmq_ctx_get (3) - get context options
zmq_getsockopt (3) - get 0MQ socket options
zmq_msg_get (3) - get message property
zmq_msg_gets (3) - get message metadata property
zmq_strerror (3) - get 0MQ error message string
zshcompwid (1) - zsh completion widgets
# ...
# a very, very, long list because of "get"
Unless -e is given, each argument is treated as a regular expressions. For example:
$ apropos 'u?limit'
setrlimit (2) - get/set resource limits
setrlimit (3p) - control maximum resource consumption
timeout (1) - run a command with a time limit
ugetrlimit (2) - get/set resource limits
ulimit (1p) - set or report file size limit
getmsg (2) - unimplemented system calls
ulimit (3) - get and set user limits
ulimit (3p) - get and set process limits
ulimit.h (0p) - ulimit commands
