getopts not working - bash

Question

I am writing a bash script which accept parameters. I am using getopts to achieve it.

#!/bin/bash

while getopts ":a" opt; do
  case $opt in
    a)
      echo "-a was triggered!" >&2
      ;;
    \?)
      echo "Invalid option: -$OPTARG" >&2
      ;;
  esac
done

but above code return's me this error.

'etOpts_test.sh: line 4: syntax error near unexpected token `in
'etOpts_test.sh: line 4: `  case $opt in

I am using CentOs 5.5

Answer 1

At line 4 you probably want case "$opt" in (quote $opt). Otherwise if it contains a metacharacter it could fail.

Answer 2

It should be a:, not :a to denote a flag requiring an argument, also question mark should not be quoted as it serves as wildcard symbol. Overall code would be (also demonstrating a flag -h not taking arguments):

function usage {
  echo "usage: ..."
}

a_arg=
while getopts a:h opt; do
  case $opt in
    a)
      a_arg=$OPTARG
      ;;
    h)
      usage && exit 0
      ;;
    ?)
      usage && exit 2
      ;;
  esac
done