I want to test if an augment (e.g. -h) was passed into my bash script or not.
In a Ruby script that would be:
#!/usr/bin/env ruby puts "Has -h" if ARGV.include? "-h" How to best do that in Bash?
- possible duplicate of bash shell script check input argumentThomas– Thomas2013-10-11 08:12:53 +00:00Commented Oct 11, 2013 at 8:12
- @Thomas -- that checks if any argument exists -- I think this question asks if a specific argument existsSoftware Engineer– Software Engineer2017-05-05 13:49:02 +00:00Commented May 5, 2017 at 13:49
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4 Answers
The simplest solution would be:
if [[ " $@ " =~ " -h " ]]; then echo "Has -h" fi 2 Comments
Cecil Curry
While clever, this reports false positives for arguments that are strings embedding the substring ` -h ` (e.g.,
my_command "oh gods -h game over"). The only general-purpose solution is to iterate getopts results as detailed below. </shrug>
kitingChris
true! Today I also would endorse getopts. The simple solution is more a wonky hack...
#!/bin/bash while getopts h x; do echo "has -h"; done; OPTIND=0 As Jonathan Leffler pointed out OPTIND=0 will reset the getopts list. That's in case the test needs to be done more than once.
3 Comments
Jonathan Leffler
The option is not removed. The trick to reparsing the argument list is to reset
OPTIND=0 between the getopts loops.
Aleksandr Levchuk
Understood. Verified. Answer corrected. Thanks to Jonathan Leffler for all the tips that lead to this answer.
logidelic
Note that for me this outputs "has -h" multiple times, even though
-h was only specified once as an argument...It is modestly complex. The quickest way is also unreliable:
case "$*" in (*-h*) echo "Has -h";; esac Unfortunately that will also spot "command this-here" as having "-h".
Normally you'd use getopts to parse for arguments that you expect:
while getopts habcf: opt do case "$opt" in (h) echo "Has -h";; ([abc]) echo "Got -$opt";; (f) echo "File: $OPTARG";; esac done shift (($OPTIND - 1)) # General (non-option) arguments are now in "$@" Etc.
answered Jun 2, 2011 at 22:56
Jonathan Leffler
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Comments
I'm trying to solve this in a straightforward but correct manner, and am just sharing what works for me.
The dedicated function below solves it, which you can use like so:
if [ "$(has_arg "-h" "$@")" = true ]; then # TODO: code if "-h" in arguments else # TODO: code if "-h" not in arguments fi This function checks whether the first argument is in all other arguments:
function has_arg() { ARG="$1" shift while [[ "$#" -gt 0 ]]; do if [ "$ARG" = "$1" ]; then echo true return else shift fi done echo false } 