Using getopts inside a Bash function

Question

I\'d like to use getopts inside a function that I have defined in my .bash_profile. The idea is I\'d like to pass in some flags to this function to alter its be

Answer 1

Here is simple example of getopts usage within shell function:

#!/usr/bin/env bash
t() {
  local OPTIND
  getopts "a:" OPTION
  echo Input: $*, OPTION: $OPTION, OPTARG: $OPTARG
}
t "$@"
t -a foo

Output:

$ ./test.sh -a bc
Input: -a bc, OPTION: a, OPTARG: bc
Input: -a foo, OPTION: a, OPTARG: foo

As @Adrian pointed out, local OPTIND (or OPTIND=1) needs to be set as shell does not reset OPTIND automatically between multiple calls to getopts (man bash).

The base-syntax for getopts is:

getopts OPTSTRING VARNAME [ARGS...]

and by default, not specifying arguments is equivalent to explicitly calling it with "$@" which is: getopts "a:" opts "$@".

In case of problems, these are the used variables for getopts to check:

• OPTIND - the index to the next argument to be processed,
• OPTARG - variable is set to any argument for an option found by getopts,
• OPTERR (not POSIX) - set to 0 or 1 to indicate if Bash should display error messages generated by the getopts.

Further more, see: Small getopts tutorial at The Bash Hackers Wiki