#compdef id gid

local args choices

if _pick_variant gnu=GNU $OSTYPE --version; then
  choices='--help --version -Z --context -g --group -G --groups -u --user'
  _arguments \
    "($choices)"{-Z,--context}'[print only security context]' \
    "($choices)"{-g,--group}'[print only EGID]' \
    "($choices -r --real)"{-G,--groups}'[print all GIDs]' \
    '(-n --name --help --version)'{-n,--name}'[show name instead of number]' \
    '(-r --real -g --groups --help --version)'{-r,--real}'[show real ID instead of effective]' \
    "($choices)"{-u,--user}'[print only EUID]' \
    '(-z --zero --help --version)'{-z,--zero}'[delimit entries with NUL characters]' \
    '(- :)--help[display help information]' \
    '(- :)--version[display version]' \
    ':user:_users'
else
  choices="-A -a -c -G -g -M -p -P -R -u"
  args=(
    "($choices)-g[print only EGID]"
    "($choices -r)-G[print all GIDs]"
    "($choices)-u[print only EUID]"
    '(-A -c -M -P)-n[show name instead of number]'
    '(-A -c -M -P)-r[show real ID instead of effective]'
  )
  case $OSTYPE in
    solaris*)
      args+=(
        '(-g -G -u -n -r)-a[show user name, user ID and all the groups]'
	'(-g -G -u -n -r)-p[show project membership]'
      )
    ;;
    openbsd*)
      args+=(
        '(-)-c[display the login class]'
        '(-)-p[make the output human readable]'
        '(-)-R[display the routing table of the current process]'
      )
    ;;
    darwin*|dragonfly*|freebsd*)
      args+=( '(-)-P[print id in the form of a password file entry]' )
    ;|
    darwin*|freebsd*)
      args+=(
	'(-)-A[print process audit user ID]'
	'(-)-M[print MAC label of the current process]'
      )
    ;|
    freebsd*) args+=( '(-)-c[print current login class]' ) ;|
    darwin*|dragonfly*|freebsd*|netbsd*|openbsd*)
      args+=( '(-)-p[human readable output]' )
    ;;
  esac
  _arguments -s $args ':user:_users'
fi