Q. How do I find UNIX / Linux command for particular task?
A. You can do keyword based search under Linux / UNIX using man or apropos command.
apropos command
Each Linux / UNIX / BSD manual page has a short description available within it. apropos command searches the descriptions for instances of keyword. keyword is usually a regular expression (-r option), wildcards (-w option), or match the exact keyword (-e option). Using these options, it may be necessary to quote the keyword or escape (\) the special characters to stop the shell from interpreting them.
apropos examples
Find out all delete / removal related administrative commands:
$ apropos -s8 -w "*delete*"
Sample output:
addgroup (8cn) - add and delete newsgroups, locally only delgroup (8cn) - add and delete newsgroups, locally only groupdel (8) - delete a group userdel (8) - delete a user account and related files
The -s option search only the given manual section. If section 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 section has an extension, for example “3perl”, then the list will only include pages in that exact part of the manual section. Following table highlights man page sections:
| Section | Meaning |
| 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] |
Find command that removes file:
$ apropos -r 'remove file'
Sample output:
rm (1) - remove files or directories
Search the short descriptions and manual page names for the keyword printf as regular expression:
$ apropos -r printf
Output:
aa_printf (3) - print text to AA-lib output buffers. asprintf (3) - print to allocated string cucul_printf (3caca) - (unknown subject) dprintf (3) - print to a file descriptor fprintf (3) - formatted output conversion fwprintf (3) - formatted wide-character output conversion gl_printf (3) - write formatted output in graphic mode printf (1) - format and print data printf (3) - formatted output conversion snprintf (3) - formatted output conversion sprintf (3) - formatted output conversion swprintf (3) - formatted wide-character output conversion vasprintf (3) - print to allocated string vdprintf (3) - print to a file descriptor vfprintf (3) - formatted output conversion vfwprintf (3) - formatted wide-character output conversion vprintf (3) - formatted output conversion vsnprintf (3) - formatted output conversion vsprintf (3) - formatted output conversion vswprintf (3) - formatted wide-character output conversion vwprintf (3) - formatted wide-character output conversion wprintf (3) - formatted wide-character output conversion
Read apropos man page for more information:
$ man apropos
Related: Linux commands to help you navigate
3 comment
Hi
Super and very useful things i am getting here..
Thanxs a lottttttttttttttt…
good website…. knowledge centr anyone can easily understand and use it
Thanks you for the apropos cmd.
Usually, I used “man -k keywordhere” but apropos looks really much nicer.
Thank you for this information… I never knew this was possible. I have always Googled through online man pages. This is much more efficient.
I have now set up an alias with a note to this page. Thanks again!