Handling long-options with getopts

4 votes
2 answers
16856 views
                          I am parsing options with getopts but would like to handle long-options as well.

    print-args ()
    {
     title="$1" ; shift
     printf "\n%s\n" "${title}: \$@:"
     for arg in "$@"; do
       (( i = i + 1 ))
       printf "%s |%s|\n" "${i}." "$arg"
     done
    }

    getopts_test ()
    {
     aggr=()
     for arg in "$@"; do
       case $arg in
        ("--colour"|"--color")     aggr+=( "-c" ) ;;
        ("--colour="*|"--color="*) aggr+=( "-c" "${arg#*=}" ) ;;
        (*)  aggr+=( "$arg" ) ;;
       esac
     done
    
     print-args "print" "$@"

     eval set -- "${aggr[@]}"
     print-args "eval" "$@"
 
     set -- "${aggr[@]}"
     print-args "set" "$@"

     local OPTIND OPTARG
     local shortopts="C:"
     while getopts "$shortopts" arg; do
       case $arg in
        ("c") context="$OPTARG" ;;
        (*) break ;;
       esac
     done
     shift $(( OPTIND - 1 ))
    }

But I wonder whether the use of set -- "${aggr[@]}" is correct.

Or is the following (using eval) more appropriate?

    eval set -- "${aggr[@]}"


I have performed a test shown below.  With eval, the string "Gunga Din" is split up, whereas with set -- "${aggr[@]}", it is being parsed correctly as a single string.

    getopts_test -f -g 130 --colour="170 20" "Gunga Din"
    
    print: $@:
    1. |-f|
    2. |-g|
    3. |130|
    4. |--colour=170 20|
    5. |Gunga Din|
    
    eval: $@:
    1. |-f|
    2. |-g|
    3. |130|
    4. |-c|
    5. |170|
    6. |20|
    7. |Gunga|
    8. |Din|
    
    set: $@:
    1. |-f|
    2. |-g|
    3. |130|
    4. |-c|
    5. |170 20|
    6. |Gunga Din|

Then I ran another function that uses the non-GNU getopt. 

    getopt_test ()
    {
     shortopts="Vuhv::H::w::e::n::l::C:"
     shortopts="${shortopts}bgcrmo"
     longopts="version,usage,help,verbosity::"
     longopts="${longopts},heading::,warning::,error::"
     longopts="${longopts},blu,grn,cyn,red,mgn,org"
     
     opts=$( getopt -o "$shortopts" -l "$longopts" -n "${0##*/}" -- "$@" )
    
     print-args "\$@:" "$@"
     print-args "opts:" "$opts"
    
     set -- "$opts"
     print-args "set -- \"$opts\"" "$@"
    
     eval set -- "$opts"
     print-args "eval set -- \"$opts\"" "$@"
    
    }

This resulted in the following

    getopt_test --warning=3 "foo'bar" "Gunga Din"
    
    $@:
    1. |--warning=3|
    2. |foo'bar|
    3. |Gunga Din|
    
    opts:
    1. | --warning '3' -- 'foo'\''bar' 'Gunga Din'|
    
    set -- "$opts"
    1. | --warning '3' -- 'foo'\''bar' 'Gunga Din'|
    
    eval set -- "$opts"
    1. |--warning|
    2. |3|
    3. |--|
    4. |foo'bar|
    5. |Gunga Din|

As shown the result of getopt is a single entry with positional arguments re-arranged.  This shows the need to use eval set -- "$opts" to split the positional arguments in the opts string into five entries for option parsing and processing.
                        
Asked by Vera (1363 rep)
Oct 30, 2021, 09:46 AM
Last activity: Dec 18, 2023, 04:43 PM
Handling long-options with getopts

Related Questions
