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What do you use to support command-line arguments for BASH scripts?

What do you use to support command-line arguments in BASH scripts?

I have a script I want to add command-line arguments to. The platforms I need it to run on are Linux and OS X.

The script-in-progress is currently here:

https://gist.github.com/duganchen/7d...311e814d090ab4

I did google, but the results were honestly kind of overwhelming.

I did find ArgBash, but honestly, I'm currently leaning towards getopts.

What does this forum recommend?

I use getopts.

Gah! That's what I get from posting at work.

I use getopt, which is a GNU beast.

Code:

info getopt

will provide some details.

I used getopts with a case statement.

https://github.com/bassmadrigal/scri...aster/sbgen.sh

Code:

while getopts "hfw:d:m:D:M:r:" OPTION

do

  case $OPTION in

    h ) help; exit

        ;;

    f ) FORCE=yes

        ;;

    w ) HOMEPAGE=$OPTARG

        ;;

    d ) DOWNLOAD=$OPTARG

        ;;

    m ) MD5SUM=$OPTARG

        ;;

    D ) DOWNLOAD64=$OPTARG

        ;;

    M ) MD5SUM64=$OPTARG

        ;;

    r ) REQUIRES=$OPTARG

        ;;

    * ) help; exit

        ;;

  esac

done

shift $(($OPTIND - 1))

I am very happy with shflags. https://github.com/kward/shflags

I think internally it uses getopts as well, but eventually you don't have to do any parsing, and just check or use the parameters as entered.

jlinkels

I never got on with getopts: it doesn't handle gnu style long-options, nor options with optional arguments, and from what I've read its use can also differ between implementations.

I usually just code the option parsing manually, no surprises that way.

Here is a simple portable example.

Code:

help='some help and documentation

  can go here'



while [ $# -gt 0 ]; do

  option="$1"; shift

  case "$option" in

    -- ) break ;;

    -f|--foo ) echo 'foo' ;;

    -b|--bar ) echo 'bar' ;;

    -h|--help ) echo "$help"; exit 0 ;;

    * ) echo "Unrecognized option '$option', use -h for help."; exit 1 ;;

  esac

done

Quote:

Originally Posted by GazL (Post 5873089)

coding the option parsing with case-esac and builtin getopts is hardly shorter than coding it completely manually, and does not seem to have any benefits.
nevertheless i've always been using it, just because it's built into bash.
i should try getopt some day.

Even when allowing for POSIX utility syntax conventions such as option combining it's really not hard to code manually, and as you say, it's not that much more long-winded or complex than the case statements employed by getopt(s).

Here's an example I wrote a few years back that follows -- to the best of my understanding -- all the POSIX guidelines, while also including support for GNU long-options. Not including the help, there are 3 example options (each in both long and short form): one with a mandatory argument, one with an optional argument and one without any argument (a basic flag). It uses no external utilities and no bashisms, just basic shell features.

Code:

#!/bin/sh



# Example of parsing command-line options/arguments.



########################################################################

usage()

{

  bs=$(tput bold) ; be=$(tput sgr0)

  cat <<-EOF



        ${bs}SYNOPSIS${be}



            options_sh [-v] [-f option_argument] [-l[option_argument]]

                [--] [operand...]

            options_sh [-?|--help]



        ${bs}DESCRIPTION${be}



            -?

            --help

                Show this usage information and exit.



            -v | --verbose

                Basic flag style option: takes no arguments.



            -f <argument>

            --file=<argument>

                Option that requires an argument.



            -l[n]

            --log[=n]

                Option that takes an optional argument (default: n=1 ).



        EOF

}



########################################################################

# Parse Option Args:



od_log="1"  # Option argument default for "LOG".



unset o_file o_log o_verbose

while [ $# -gt 0 ]

do

  case "$1" in

    --)          shift ; break ;;

    -|""|[!-]*)  break ;;

    -\?|--help)  usage ; exit 0 ;;

    --file=*)    o_file="${1#*=}" ;;

    --log)        o_log="$od_log" ;;

    --log=*)      o_log="${1#*=}" ;;

    --verbose)    o_verbose=1 ;;

    --*)          echo "unknown long option: $1" >&2 ;;

    -?*)          # short options:

                  opts="${1#-}"

                  while [ "${opts}" ]

                  do

                    nopts=${opts#?}

                    opt=${opts%${nopts}}

                    case "${opt}" in

                      v)  o_verbose=1 ;;

                      f)  if [ "${nopts}" ]; then

                            o_file="${nopts}"

                            nopts=""

                          else 

                            o_file="${2:?'-f' option expects filename argument!}"

                            shift

                          fi

                          ;;

                      l)  if [ "${nopts}" ]; then

                            o_log="${nopts}"

                            nopts=""

                          else 

                            o_log="${od_log}"

                          fi

                          ;;

                      ?)  echo "Invalid option: ${opt}" >&2 ; exit 1 ;;

                    esac

                    opts=${nopts}

                  done

                  ;;

  esac

  shift

done



########################################################################

# Validate input options/arguments:



  # Validate your input here. I find it best to keep parsing and

  # validation as two separate activities, otherwise the code

  # tends to get unwieldy.



########################################################################

# Rest of script:



[ "$o_verbose" ]  &&  echo "VERBOSE Selected"

[ "$o_file" ]    &&  echo "file: $o_file"

[ "$o_log" ]      &&  echo "LOG Selected, Value is: $o_log"





while [ $# -gt 0 ]

do

  echo "Operand: $1"

  shift

done



################################################################# End. #

Anyway, fwiw, that's my basic options boilerplate.

Quote:

Originally Posted by dugan (Post 5873064)

Did you examine the BASH man page sections on command line arguments? Everything you really need is there.

Thanks all. I went with getopts.

The finished script is here:

https://github.com/duganchen/md_preview