zsh/Completion/User/_init_d

#compdef -P */(init|rc[0-9S]#).d/*

local magic cmds what

# This should probably be system specific...

# If the file starts with `#!' we hope that this is a shell script
# and get lines looking like <space>foo|bar) with the words in $what.

what='(st(art|op|atus)|(force-|)re(start|load)|debug_(up|down)|dump(|_stats)|add|delete|clean|list)'

read -u0k 2 magic < $words[1] && [[ $magic = '#!' ]] &&
    cmds=( ${${(j:|:s:|:)${(M)${(f)"$(< $words[1])"}:#[[:blank:]]#(\'|)${~what}(|${~what})#(\'|)\)}}//[^a-z_]} )

# This would be the pattern to use every line of the form <space>foo).
# Some people say this might match too many lines...
#
#    cmds=( ${${(j:|:s:|:)${(M)${(f)"$(< $words[1])"}:#[[:blank:]]#(\'|)[a-z_|]##(\'|)\)}}//[^a-z_]} )

(( $#cmds )) || zstyle -a ":completion:${curcontext}:commands" commands cmds ||
    cmds=(start stop)

_sub_commands $cmds