man allows users to format/display the user “manual” that is built into Linux. This manual holds a catalogue of commands and other aspects of the Linux OS.

$ man [command]
$ man ls
$ man strcmp

Useful Examples

man png

$ man png
PNG(5)                   File Formats Manual                  PNG(5)

       png - Portable Network Graphics (PNG) format
Break it down
  • Typically, you can enter the name of a user command after man, but it is also possible to use man to learn about file extensions, such as png.
  • Not only are user commands and file extentions built in to the manual, but also system calls, library functions, special files, games, math library functions, a tcl function, and other miscellaneous categories.

man 3 printf

$ man 3 printf
printf(3)                   BSD Library Functions Manual                  printf(3)

    printf, fprintf, sprintf, snprintf, asprintf, dprintf, vprintf,
    vfprintf, vsprintf, vsnprintf, vasprintf, vdprintf -- formatted
    output conversion
Break it down
  • Most commands/functions are unique, but there are cases where a command/function has multiple versions.
  • 3 refers to the third section’s printf function. There is another version in section 1. If the 3 was not specified (man printf), man would automatically open up the lowest numbered section, causing some confusion.

man -a printf

$ man -a printf
Break it down
  • Similar to the last example, printf is a function with many versions. Sometimes, a user may not know that there are multiple versions to a command/function.
  • -a forces man to display all manual pages for printf, not just the first one in the lowest numbered section.

man -k .

$ man -k .
ldap.conf (5)        - LDAP configuration file/environment variables
adduser.conf (5)     - configuration file for adduser(8) and addgroup(8) .
anacrontab (5)       - configuration file for anacron
subdomain.conf (5)   - configuration file for fine-tuning the behavior of the...
deluser.conf (5)     - configuration file for deluser(8) and delgroup(8) .
hosts.equiv (5)      - list of hosts and users that are granted "trusted" r c...
mailcap.order (5)    - the mailcap ordering specifications
modules (5)          - kernel modules to load at boot time
interfaces (5)       - network interface configuration for ifup and ifdown
updatedb.conf (5)    - a configuration file for updatedb(8)
slabinfo (5)         - kernel slab allocator statistics
Break it down
  • This command lets you see a list of all man pages
  • -k is the apropos command, which lets you search the manual page names and descriptions
  • The . is a regex that means “any character”
  • Additonally, since man pages are divided into sections, typing man -k . -s 2 will list all man pages within section 2.

man [command] | col -x -b | groff -man -Tps >

$ man [command] | col -x -b | groff -man -Tps >
Break it down
  • In some cases, it is helpful to print out a man page so you have a hard copy handy. This command will format the man page and output it as a .ps file, which is print-ready
  • man [command] is your typical man command, which will get piped into other useful user commands that perform text formatting
  • col -x -b filters reverse line feeds from the piped man input. -b prints only the last character written to each column position (no backspaces). -x outputs multiple spaces instead of tabs.
  • groff -man -Tps will perform front-end formatting for documents. man ensures the traditional man page format. -T sets the output device to a specified format; in this case, we have specified the output to ps. However, other supported files include ascii, cp1047, dvi, html, latin1, lbp, lj4, utf8, X75, and X100.
  • is the file name that the formatted text will be outputed to. Make sure the format is the same as what is specified in groff.