Linux: Finding all the members of a group

Finding all the members of a group is an occasional requirement and while there are a number of ways to do this by parsing the /etc/group and /etc/password files, Debian/Ubuntu come with a simpler solution that performs all this skulduggery for you. This is the members function that can simply be installed using sudo apt-get install members . Once this is done, members of a group named foo can be listed using:
members foo.

The function also supports a few options to differentiate between primary and secondary group members. The man page is as follows:

MEMBERS(1)

NAME
       members - outputs members of a group

SYNOPSIS
       members groupname

DESCRIPTION
       This manual page documents briefly the members commands.  This manual page was written for the Debian GNU/Linux distribution.

       members is a program that sends a space-separated list of secondary member names to its standard output.

OPTIONS
       The programs follow the usual GNU command line syntax, with long options starting with two dashes (`-').  A summary of options is included below.

       -a, --all
              Show all group members on one line. This is the default.

       -p, --primary
              Show only primary group members.

       -s, --secondary
              Show only secondary group members.

       -t, --two-lines
              Send two lines to standard output. First line is primary members, second line is secondary members. NOTE: This always displays two lines, even if there are no members at all.

       -h, --help
              Show summary of options.

I'm not sure if this package is available for other distributions. It probably is.

Hope this helps.