bash script parameters

Question

I need to write a bash script, and would like it to parse unordered parameters of the format:

scriptname --param1 <string> --param2 <string> --param3 <date>

Is there a simple way to accomplish this, or am I pretty much stuck with $1, $2, $3?

score 10 · Accepted Answer · answered May 06 '09 at 02:55

10

You want getopts.

answered May 06 '09 at 02:55

Lance Richardson

4,610
23
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5

getopts doesn't support long switches (starting with --). getopt does, but it is pretty horrible to use/read – Cameron May 06 '09 at 02:56
Good point - if long switches are a must-have, getopts isn't the right tool. – Lance Richardson May 06 '09 at 03:00
3

This answer would be better with content and or example, instead of just a link. – Vincent Scheib Mar 12 '13 at 18:55

lhunath · Answer 2 · 2014-08-09T09:48:16.477

8

while [[ $1 = -* ]]; do
    arg=$1; shift           # shift the found arg away.

    case $arg in
        --foo)
            do_foo "$1"
            shift           # foo takes an arg, needs an extra shift
            ;;
        --bar)
            do_bar          # bar takes no arg, doesn't need an extra shift
            ;;
    esac
done

edited Aug 09 '14 at 09:48

answered May 06 '09 at 08:45

lhunath

120,288
16
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Shouldn't do_foo "$2" be do_foo "$1"? – xx77aBs Aug 08 '14 at 09:20
@xx77aBs yes, it should! – lhunath Aug 09 '14 at 09:48

score 2 · Answer 3 · 2011-09-29T12:42:36.117

2

A nice example of how to implement short & long switches side by side is mcurl:

http://www.goforlinux.de/scripts/mcurl/

edited Sep 29 '11 at 12:42

answered May 07 '09 at 10:00

score 1 · Answer 4 · answered May 06 '09 at 03:05

Bash has a getops function, as mentioned here before, that might solve your problems.

If you need anything more sophisticated, bash also supports positional parameters (ordered $1 ... $9, and then ${10} .... ${n}), you'll have to come up with your own logic to handle this input. One easy way to go is to put a switch/case inside of a for loop, iterating over the parameters. You can use either one of the two special bash vars that handle the input: $* or $@.

score -1 · Answer 5 · answered Jan 22 '16 at 17:39

#!/bin/bash

# Parse the command-line arguments
while [ "$#" -gt "0" ]; do
  case "$1" in
    -p1|--param1)
      PARAM1="$2"
      shift 2
    ;;
    -p2|--param2)
      PARAM2="$2"
      shift 2
    ;;
    -p3|--param3)
      PARAM3="$2"
      shift 2
    ;;
    -*|--*)
      # Unknown option found
      echo "Unknown option $1."

      exit 1
    ;;  
    *)
      CMD="$1"
      break
    ;;
  esac
done 


echo "param1: $PARAM1, param2: $PARAM2, param3: $PARAM3, cmd: $CMD"

When I execute this:

./<my-script> --param2 my-param-2 --param1 myparam1 --param3 param-3 my-command

it outputs what you expect:

param1: myparam1, param2: my-param-2, param3: param-3, cmd: my-command

bash script parameters

5 Answers5