Provide two arguments to one option using getopts

Question

In below code when I give option r then getopts requires one arguments:

while getopts ":hr::l:" opt; do
    case $opt in
        r ) echo "Run Numbers - argument = $OPTARG " ;;
        l ) echo "Latency range - argument = $OPTARG" ;;
        h ) helptext
            graceful_exit ;;
        * ) usage
            clean_up
            exit 1
    esac
done

But I need to pass two arguments after -r option, instead of one. Is there an easy way to do this?

Solution

You cannot pass two arguments with single option using getopts.

I recommend the following alternatives:

1. Put quotes around multiple arguments

   In this case getopts will treat them as one argument, but you will be able to split it later on. You can even put all arguments in the array at once:

   #!/bin/bash  
   
   while getopts ":hr:l:" opt; do
       case $opt in
           r ) echo "Run Numbers - argument = $OPTARG "
               set -f # disable glob
               IFS=' ' # split on space characters
               array=($OPTARG) ;; # use the split+glob operator
           l ) echo "Latency range - argument = $OPTARG" ;;
           h ) helptext
               graceful_exit ;;
           * ) usage
               clean_up
               exit 1
       esac
   done
   
   echo "Number of arguments: ${#array[@]}"
   echo -n "Arguments are:"
   for i in "${array[@]}"; do
     echo -n " ${i},"
   done
   printf "\b \n"
   

   The example of run:

   ./script -r "123 456 789"
   

   And output:

   Run Numbers - argument = 123 456 789 
   Number of arguments: 3
   Arguments are: 123, 456, 789
   

2. Use comma (or other preferred character) as a delimiter

   ./script -r 123,456,789
   

   and you just replace IFS=" " with IFS=, in the code above. That one has the advantage of allowing empty elements. As pointed out in the comments section this solution is chosen by some common programs e.g. lsblk -o NAME,FSTYPE,SIZE.

3. Allow multiple -r options

   Multiple -r, but each taking only one argument:

   ./script -r 123 -r 456 -r 789
   

   Then arguments would be added to array one by one

   array+=("$OPTARG")
   

   That one has the advantage of not having limitations on what characters the elements may contain. This one is also used by some standard linux tools e.g. awk -v var1=x -v var2=y.

Comments

[PM 2Ring]

The comma delimiter idea is good, as it's used by various standard commands, notably mount.

[jimmij]

Possible, one can still transform this "delimited" form into array with array=(${OPTARG//,/ }). Yet another possibility is to just use multiple times -r arg option each time adding element to an array array+=($OPTARG).

[PM 2Ring]

Even easier: IFS=',' array=($OPTARG)

[Volker Siegel]

Examples: pgrep uses comma: ps -s 123,456 ..., grep uses repeating the option: grep -e pattern1 -e pattern2 ... (-e is optional when only one pattern is used).

[ctrl-alt-delor]

you don't want to make the user do more work e.g. put quotes around the list, just because of a limitation in the language/library you are using. However the use of , seems reasonable, even preferable to the use of a space.