members

A patched drop-in replacement of members(1), a tool for finding users in a group.

Examples

$ members audio
speech-dispatcher pulse george
$ members -p audio
speech-dispatcher
$ members -s audio
pulse george
$ members -t audio
speech-dispatcher
pulse george

Motivation

I started using members(1) to help verify an OpenLDAP directory, but its output did not seem plausible. I took a look at the source, and noticed a glaring bug causing the first primary member of a group (in terms of getent passwd) to always be missed out:

if(theGroup)
  {
    struct passwd *thePasswd;

    setpwent();

    thePasswd = getpwent();

    if(thePasswd)
  {   
    thePasswd = getpwent();  // overwrites the first entity
    
    while(thePasswd)
      {
        // ...
        
        thePasswd = getpwent();
      }
  }

    endpwent();

    // ...
  }

Instead of creating a patch, I realised I'd stumbled across a languishing package not modified since 2008, with a man page not touched since 1999. It was 363 lines of C++ written in the style of C, with negative indentation and lots of unnecessary complexity (especially with regard to options parsing). So I rewrote it.

This repository is the result. I used pure, modern C to match the underlying APIs (pwd.h, grp.h). Ignoring documentation (which the original was heavily lacking), code footprint has simultaneously been reduced by 35% to 235 lines.

Usage

$ members --help
Usage: members [OPTION]... GROUP
Show members of a group.

members(1) is the complement of groups(1): where groups(1) shows the groups a
user belongs to, members(1) shows users belonging to a group.

  -p, --primary              show only members for which GROUP is their
                               primary group
  -s, --secondary            show only members who have a secondary
                               membership in GROUP
  -t, --two-lines            show primary members on the first line of output
                               and secondary members on the second line; two
                               lines are always printed
  -h, --help                 display this help and exit
  -v, --version              output version information and exit

Exit status:
 0  OK
 1  input error (e.g. no GROUP, unrecognised flag)
 2  GROUP does not exist
 3  GROUP exists but could not be opened (see error message)
 4  GROUP did not have any members