Shell long-options

bash-long-options.sh

#!/bin/bash

SERVER=''
SHORT_PARAM='-s'        # short option name
LONG_PARAM='--server'   # long option name

while [ $# -gt 0 ]; do
    case "${1}" in
        $SHORT_PARAM=*|$SHORT_PARAM*|$LONG_PARAM=*|$LONG_PARAM)  ## matches both`[-s|--server]=value` and `[-s|--server] value`
            param="${1#$SHORT_PARAM}"                            ## removes `-s` from the front of $1
            param="${param#$LONG_PARAM}"                         ## removes `--server` from the front of $1

            if [ "${param:0:1}" == = ]; then                     ## if there is a `=` as the first char
                param=${param:1}                                 ## removes `=`. this acts like an slice (goland) and list range (python)
                                                                 ## the value is the rest of $1, after the `=`
            elif [ -z "${param:0:1}" ]; then
                shift                                            ## otherwise, the value is the next parameter ($2). `shift` "eats" $1
                param=$1                                         ## and the new `$1` is nown the former `$2`.
            fi

            SERVER="$param"                                      ## save the value for future use
        ;;
        *) echo Invalid parameter: $1
    esac
    shift
done

echo SERVER=$SERVER

# Tests:
# $ for i in -sbastion -s=bastion '-s bastion' --server=bastion '--server bastion'; do
#   /tmp/params.sh $i
# done
# SERVER=bastion
# SERVER=bastion
# SERVER=bastion
# SERVER=bastion
# SERVER=bastion