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I am writing scripts with the following boilerplate CLI pattern:

usage(){
  echo "$0 yada yada"
  ...
  echo 
}
for arg in "$@"; do
  case "$arg" in
    '--help|-help') set -- "$@" '-h';;
    ...
  esac
done

OPTIND=1
while getopts 'h...' opt; do
  case "$opt" in
     'h') usage; exit 0;;
      ...
  esac
done
shift $((OPTIND-1))

Is there any way to compress or encapsulate this in BASH on linux with other tools, perhaps an additional dependency?

Chris
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  • That sounds like a bad approach. If your script were grep for instance, grep -e --help -- --help is meant to look for --help in the file called --help, but you would end up transforming that to grep -e -h -- -h. Also with the standard CLI interface cmd -help is meant to be the same as cmd -h -e -l -p (or cmd -h -e lp if the -e option takes an argument, etc). See getopt, getopts or manual parsing - what to use when I want to support both short and long options? and many other Q&As here for approaches at parsing long options – Stéphane Chazelas Jul 25 '23 at 16:45
  • @StéphaneChazelas grep requires commands searching for, for example, '--help' to be escaped, grep '\-\-help', even after adding quotes, so this is beside the point, imo. Yes, there are other ways, this is a simple one and I am looking for an even simpler way. – Chris Jul 25 '23 at 16:55
  • @StéphaneChazelas yes, I am aware of that edge case -- if I define parameters -h, -e, -l, -p then a user could eventually stumble on a surprise. I am probably not going to change things for now, since the goal is for the user to stumble on help. If the edge case becomes an issue, I'll change it. – Chris Jul 25 '23 at 16:57
  • no. - is not a regex operator so putting backslash in front of it yields unspecified behaviour. To grep for --help, you use either grep -- --help file where -- marks the end of options or grep -e --help file or grep -e--help file where --help is the argument to the -e option. – Stéphane Chazelas Jul 25 '23 at 16:57
  • @StéphaneChazelas I have had to escape backslashes with grep in cross platform scripts. Surely in some contexts you are right, but it's got nothing to do with my question. In fact, I don't need to use -- --help to work with bash if I escape the dashes, and I don't need to use --regexp (-e) either. – Chris Jul 25 '23 at 16:58
  • You use backslash to escape regexp operators as in grep '\.' file to look for a literal . or to introduce some other operators, like in grep '\([[:upper:]]\{4\}\)\1' to look for a repeated sequence of 4 uppercase letters. grep '\-\-help' is just plain wrong even if in most grep implementations it will do the same as grep -e --help. – Stéphane Chazelas Jul 25 '23 at 17:01
  • @StéphaneChazelas nonetheless, I'll consider your feedback in the boilerplate I'm not sure I can qualify including due to its lack of brevity. – Chris Jul 25 '23 at 17:02
  • @StéphaneChazelas " grep '--help' is just plain wrong even if in most grep implementations it will do the same as grep -e --help" -- this feels like a matter of opinion and a rant. Please stop defacing my question. – Chris Jul 25 '23 at 17:03
  • If you use util-linux getopt or other option parsing tools/library, then you don't need to worry about all that. It will also properly handle unambiguous long option abbreviation (like --h / --he) here assuming it's the only long option that starts with h/he) and --input=foo in addition to --input foo and -ifoo + -i foo, etc. – Stéphane Chazelas Jul 25 '23 at 17:04
  • @StéphaneChazelas I'll explore getopt, thanks -- presuming it is not as ubiquitous as the getopts built-in – Chris Jul 25 '23 at 17:22

0 Answers0