3 
$ bash file.sh expected_arg -f optional_arg

I've seen posts that address using $1 to grab the first argument

and posts that address using getopts for parsing flag arguments. I haven't seen a post that addresses both.

I'm currently accessing expected_arg via $1.

I can't process the -f flag at all. Even though I also have this in my test script:

#!/bin/bash

dirname=$1

[[ -z  $dirname  ]] && echo "Project name required as an argument." && return

# get flags
verbose='false'
aflag='false'
bflag='false'
files='false'
while getopts 'abf:v' flag; do
  case "${flag}" in
    a) aflag='true' ;;
    b) bflag='true' ;;
    f) files="${OPTARG}" ;;
    v) verbose='true' ;;
    *) error "Unexpected option ${flag}" ;;
  esac
done

echo "$files"

echo "$HOME/Desktop/$dirname"

exit

The terminal shows:

Jills-MBP:~ jillr$ bash test.sh blah -f file
false
/Users/jillr/Desktop/blah

Unless I switch the order of the arguments, as in:

bash file.sh -f optional_arg expected_arg

Which the terminal outputs:

Jills-MBP:~ jillr$ bash test.sh -f file blah
file
/Users/jillr/Desktop/-f

So naturally, -f is processed as $1, which isn't what I want. I need to grab the expected_arg

Constraints needed:

  • I need to allow for a varying number of flags (from none at all to several). Therefore, the position of expected_arg will vary
  • expected_arg is a must
  • I would rather avoid having to use another flag in order to parse expected_arg (as in, I want to avoid doing something like $ bash test.sh -f file -d blah)

How can I satisfy those constraints?

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4

Nevermind. I found this post: Using getopts to parse options after a non-option argument

which basically says I can solve my issue simply by placing shift after dirname=$1

Which will allows for entering the arguments as 

$ bash file.sh expected_arg -f optional_arg
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3
  • +1, yep shift is what you need here....but it's generally better not to assume a fixed position for an argument, especially if you might have more than one non-option argument. in other words, it's better to process the options first, then you know that whatever is remaining are non-options. One of the reasons for using getopts (or getopt) is that you don't have to know the order of args, or even the number of args. Commented Aug 8, 2017 at 2:15
  • @cas feel free to post an implementation ;) :D Commented Aug 8, 2017 at 14:21
  • the implementation is your code above except you don't have dirname=$1 or the test for -z $dirname before the getopts, you have them after the getopts processing, when all that's left is non-option args. and you double-quote both $dirname and $1 too, because that's what you should do when referencing a variable (or positional parameter), especially when they come from unknown/uncontrolled sources like command-line arguments. Commented Aug 8, 2017 at 14:30

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