Extract values from an array

Question

I have an array of options and their arguments:

ARGS=('-a' '-c' 'red' 'orange' '--verbose' '-p' 'apple' 'banana')

I need to extract arguments for the option -c and get a list of the rest:

echo "${COLORS[@]}" # returns: red orange
echo "${OPTIONS[@]}" # returns: -a --verbose -p apple banana

I have managed to get a list of colors using getopts (probably not the best approach), but I didn't find a way to extract the rest of the options.

COLORS=()

set_colors() {
  while getopts "p:" option 2>/dev/null; do
    case ${option} in
      p)
        COLORS+=("$OPTARG")
        while [[ "$OPTIND" -le "$#" ]] && [[ "${!OPTIND:0:1}" != "-" ]]; do
          COLORS+=("${!OPTIND}")
          ((OPTIND++))
        done
        ;;
      *) ;;
    esac
  done
}

set_colors "${ARGS[@]}"

To be compatible with other tools, I propose to make your tool accept the command line options as -a -c red -c orange --verbose -p apply -p banana - ie. the -c flag is cumulative and needs to be specified for each color. This will make parsing arguments easier and more consistent for a small inconvenience. — KamilCuk
– KamilCuk, Commented Dec 14, 2019 at 20:27
As an aside, all-caps is used for variables that modify or reflect behavior of the shell itself and POSIX-defined tools; the standard recommends using names with at least one lower-case character in your own software to avoid inadvertently modifying behavior of standard-defined tools. (Read the linked specification keeping in mind that shell variables and environment variables share a single namespace -- modifying the former change the latter implicitly when the names match). — Charles Duffy
– Charles Duffy, Commented Dec 14, 2019 at 20:40
...and btw, I strongly agree with @KamilCuk's recommendation above. It's a widely-used convention for good reason. — Charles Duffy
– Charles Duffy, Commented Dec 14, 2019 at 20:50

choroba · Accepted Answer · 2019-12-14 20:14:19Z

1

I used the variable $in_colors as a flag when walking over the options and distributing them into two arrays.

#! /bin/bash
ARGS=('-a' '-c' 'red' 'orange' '--verbose' '-p' 'apple' 'banana')

in_colors=0
for arg in "${ARGS[@]}" ; do

    if [[ $arg == '-c' ]] ; then
        in_colors=1
    elif [[ $arg == -* ]] ; then
        in_colors=0
    fi

    if ((in_colors)) ; then
        colors+=("$arg")
    else
        opts+=("$arg")
    fi
    shift
done
echo "Colors: ${colors[@]}"
echo "Options: ${opts[@]}"

answered Dec 14, 2019 at 20:14

choroba

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