18. Shell Option Evaluation Loop¶

A generalized option evaluation loop is implemented in snippet sh_b.opt-loop. This chapter describes the algorithm employed.

18.1. Shell Commmand Grammar¶

BNF for simple scripts:

command: command-name
       | command-name options
       | command-name arguments
       | command-name options arguments

options : option
        | option options

option: option-symbol
      | option-symbol argument

BNF for script implementing a command shell:

command-shell: command-shell-name
             | command-shell-name options
             | command-shell-name command
             | command-shell-name options command

18.2. Option Loop Activity Diagram¶

18.3. Option Loop Template¶

# ::here::
opt_debug=0
opt_arg='default arg'
pass_opts=
while :
do
    test x${1+set} = xset || break
    case "${1}" in
    ## (progn (forward-line 1) (snip-insert "sh_b.opt-option" t t "sh" " --key skip_for_update --key opt-minimalx") (insert "\n"))
    # Defining opt_short as `o`, opt_long as `option`, opt_arg as `ARG` => creates option: -o, --option ARG; the value `::fillme::` is considered blank, it does not have to be removed
    # (let ((opt_short "::fillme::") (opt_long "::fillme::") (opt_arg "::fillme::")) (forward-line 2) (snip-insert "sh_b.opt-option" t t "sh" (concat " --key opt-minimalx --key skip_for_update --key opt_short --value " opt_short " --key opt_long --value " opt_long " --key opt_arg --value " opt_arg)))
    # ::here::
    -d|--d|--de|--deb|--debu|--debug) # --debug
        opt_debug=1
        pass_opts="${pass_opts}"' --debug'
        ;;
    -a|--a|--ar|--arg) # --arg OPT-ARG
        opt_arg="${2-}"
        test x"${2+set}" = xset && shift
        pass_opts="${pass_opts}"' --arg '"${opt_arg}"
        #pass_opts="${pass_opts}"' --arg '"$( single_quote_enclose "${opt_arg}" )"
        ;;
    -\?|-h|--h|--he|--hel|--help) # --help
        usage; exit 0
        pass_opts="${pass_opts}"' --help'
        ;;
    --u|--um|--uml|--umlx) # --umlx RX[:TYP]
        opt_umlx="${2-}"
        test x"${2+set}" = xset && shift
        opt_umlx_match="$( printf "%s\n" "${opt_umlx}" | ${SED__PROG-sed} 's,^\([^:]*\)\(:\([^:]*\)\)*.*,\1,' )"
        opt_umlx_type="$( printf "%s\n" "${opt_umlx}" | ${SED__PROG-sed} 's,^\([^:]*\)\(:\([^:]*\)\)*.*,\3,' )"
        out_filt_conv ()
        {
            _type="${1}"
            case "${_type}" in
            ## (progn (forward-line 1) (snip-insert "sh_b.case_patterns_for_actions" t t "sh" " --key actions --value '::fillme::'") (insert ""))
            v|vi|vie|view) _type='svg';;
            esac
            if test -z "${_type}"
            then
                cat
            else
                plantuml -t"${_type}" -pipe
            fi
        }
        out_filt_disp ()
        {
            _type="${1}"
            case "${_type}" in
            ## (progn (forward-line 1) (snip-insert "sh_b.case_patterns_for_actions" t t "sh" " --key actions --value '::fillme::'") (insert ""))
            v|vi|vie|view) _type='view';;
            esac
            if test "${_type}" != view
            then
                cat
            else
                display
            fi
        }
        (
        if test -n "${opt_umlx_match}"
        then
            line_diversion.py --match "${opt_umlx_match}" "${prog_path-${0}}"
        else
            line_diversion.py "${prog_path-${0}}"
        fi
        ) \
        | out_filt_conv "${opt_umlx_type}" \
        | out_filt_disp "${opt_umlx_type}"
        exit 0
        #pass_opts="${pass_opts}"' --umlx '"${opt_umlx}"
        #pass_opts="${pass_opts}"' --umlx '"$( single_quote_enclose "${opt_umlx}" )
        ;;
    --) # end of options
        shift; break;;
    -) # stdin
        break;;
    -*) # unknown option
        echo >&2 "${prog_name-$( basename "${0}" )}: error: unknown option \`${1}'"
        exit 1
        break
        ;;
    *)
        break;;
    esac
    shift
done

18.4. Snippet for defining an option¶

sh_b.opt-loop contains shell comments with emacs lisp code for inserting an option definiton:

;; opt_short: o | opt_long: option | opt_arg: ARG => description: -o, --option  ARG || ::fillme:: is considered blank, it does not have to be removed
(let ((opt_short "::fillme::")
      (opt_long "::fillme::")
      (opt_arg "::fillme::"))
  (forward-line 1)
  (snip-insert "sh_b.opt-option" t t "sh"
               (concat " --key opt_short --value " opt_short
                       " --key opt_long --value " opt_long
                       " --key opt_arg --value " opt_arg)))

The ::fillme:: tag is interpreted as if the parameter was blank. I.e., the ::fillme:: tags do not have to be deleted, only replaced as necessary.

18.4.1. Example options¶

18.4.1.1. No parameters¶

The following Emacs Lisp expression, which does not define any of opt_short, opt_long and opt_arg,

(progn
  (forward-line 1)
  (snip-insert "sh_b.opt-option" t t "sh"))