Using getopts to process long and short command line options

getopt and getopts are different beasts, and people seem to have a bit of misunderstanding of what they do. getopts is a built-in command to bash to process command-line options in a loop and assign each found option and value in turn to built-in variables, so you can further process them. getopt, however, is an external utility program, and it doesn't actually process your options for you the way that e.g. bash getopts, the Perl Getopt module or the Python optparse/argparse modules do. All that getopt does is canonicalize the options that are passed in — i.e. convert them to a more standard form, so that it's easier for a shell script to process them. For example, an application of getopt might convert the following:

myscript -ab infile.txt -ooutfile.txt

into this:

myscript -a -b -o outfile.txt infile.txt

You have to do the actual processing yourself. You don't have to use getopt at all if you make various restrictions on the way you can specify options:

only put one option per argument;

all options go before any positional parameters (i.e. non-option arguments);

for options with values (e.g. -o above), the value has to go as a separate argument (after a space).

Why use getopt instead of getopts? The basic reason is that only GNU getopt gives you support for long-named command-line options.¹ (GNU getopt is the default on Linux. Mac OS X and FreeBSD come with a basic and not-very-useful getopt, but the GNU version can be installed; see below.)

For example, here's an example of using GNU getopt, from a script of mine called javawrap:

# NOTE: This requires GNU getopt.  On Mac OS X and FreeBSD, you have to install this
# separately; see below.
TEMP=$(getopt -o vdm: --long verbose,debug,memory:,debugfile:,minheap:,maxheap: \
              -n 'javawrap' -- "$@")

if [ $? != 0 ] ; then echo "Terminating..." >&2 ; exit 1 ; fi

# Note the quotes around '$TEMP': they are essential!
eval set -- "$TEMP"

VERBOSE=false
DEBUG=false
MEMORY=
DEBUGFILE=
JAVA_MISC_OPT=
while true; do
  case "$1" in
    -v | --verbose ) VERBOSE=true; shift ;;
    -d | --debug ) DEBUG=true; shift ;;
    -m | --memory ) MEMORY="$2"; shift 2 ;;
    --debugfile ) DEBUGFILE="$2"; shift 2 ;;
    --minheap )
      JAVA_MISC_OPT="$JAVA_MISC_OPT -XX:MinHeapFreeRatio=$2"; shift 2 ;;
    --maxheap )
      JAVA_MISC_OPT="$JAVA_MISC_OPT -XX:MaxHeapFreeRatio=$2"; shift 2 ;;
    -- ) shift; break ;;
    * ) break ;;
  esac
done

This lets you specify options like --verbose -dm4096 --minh=20 --maxhe 40 --debugfi="/Users/John Johnson/debug.txt" or similar. The effect of the call to getopt is to canonicalize the options to --verbose -d -m 4096 --minheap 20 --maxheap 40 --debugfile "/Users/John Johnson/debug.txt" so that you can more easily process them. The quoting around "$1" and "$2" is important as it ensures that arguments with spaces in them get handled properly.

If you delete the first 9 lines (everything up through the eval set line), the code will still work! However, your code will be much pickier in what sorts of options it accepts: In particular, you'll have to specify all options in the "canonical" form described above. With the use of getopt, however, you can group single-letter options, use shorter non-ambiguous forms of long-options, use either the --file foo.txt or --file=foo.txt style, use either the -m 4096 or -m4096 style, mix options and non-options in any order, etc. getopt also outputs an error message if unrecognized or ambiguous options are found.

NOTE: There are actually two totally different versions of getopt, basic getopt and GNU getopt, with different features and different calling conventions.² Basic getopt is quite broken: Not only does it not handle long options, it also can't even handle embedded spaces inside of arguments or empty arguments, whereas getopts does do this right. The above code will not work in basic getopt. GNU getopt is installed by default on Linux, but on Mac OS X and FreeBSD it needs to be installed separately. On Mac OS X, install MacPorts (http://www.macports.org) and then do sudo port install getopt to install GNU getopt (usually into /opt/local/bin), and make sure that /opt/local/bin is in your shell path ahead of /usr/bin. On FreeBSD, install misc/getopt.

A quick guide to modifying the example code for your own program: Of the first few lines, all is "boilerplate" that should stay the same, except the line that calls getopt. You should change the program name after -n, specify short options after -o, and long options after --long. Put a colon after options that take a value.

Finally, if you see code that has just set instead of eval set, it was written for BSD getopt. You should change it to use the eval set style, which works fine with both versions of getopt, while the plain set doesn't work right with GNU getopt.

¹Actually, getopts in ksh93 supports long-named options, but this shell isn't used as often as bash. In zsh, use zparseopts to get this functionality.

²Technically, "GNU getopt" is a misnomer; this version was actually written for Linux rather than the GNU project. However, it follows all the GNU conventions, and the term "GNU getopt" is commonly used (e.g. on FreeBSD).

---

There are three implementations that may be considered:

Bash builtin getopts. This does not support long option names with the double-dash prefix. It only supports single-character options.

BSD UNIX implementation of standalone getopt command (which is what MacOS uses). This does not support long options either.

GNU implementation of standalone getopt. GNU getopt(3) (used by the command-line getopt(1) on Linux) supports parsing long options.

Some other answers show a solution for using the bash builtin getopts to mimic long options. That solution actually makes a short option whose character is "-". So you get "--" as the flag. Then anything following that becomes OPTARG, and you test the OPTARG with a nested case.

This is clever, but it comes with caveats:

getopts can't enforce the opt spec. It can't return errors if the user supplies an invalid option. You have to do your own error-checking as you parse OPTARG.

OPTARG is used for the long option name, which complicates usage when your long option itself has an argument. You end up having to code that yourself as an additional case.

So while it is possible to write more code to work around the lack of support for long options, this is a lot more work and partially defeats the purpose of using a getopt parser to simplify your code.

---

The Bash builtin getopts function can be used to parse long options by putting a dash character followed by a colon into the optspec:

#!/usr/bin/env bash 
optspec=":hv-:"
while getopts "$optspec" optchar; do
    case "${optchar}" in
        -)
            case "${OPTARG}" in
                loglevel)
                    val="${!OPTIND}"; OPTIND=$(( $OPTIND + 1 ))
                    echo "Parsing option: '--${OPTARG}', value: '${val}'" >&2;
                    ;;
                loglevel=*)
                    val=${OPTARG#*=}
                    opt=${OPTARG%=$val}
                    echo "Parsing option: '--${opt}', value: '${val}'" >&2
                    ;;
                *)
                    if [ "$OPTERR" = 1 ] && [ "${optspec:0:1}" != ":" ]; then
                        echo "Unknown option --${OPTARG}" >&2
                    fi
                    ;;
            esac;;
        h)
            echo "usage: $0 [-v] [--loglevel[=]<value>]" >&2
            exit 2
            ;;
        v)
            echo "Parsing option: '-${optchar}'" >&2
            ;;
        *)
            if [ "$OPTERR" != 1 ] || [ "${optspec:0:1}" = ":" ]; then
                echo "Non-option argument: '-${OPTARG}'" >&2
            fi
            ;;
    esac
done

After copying to executable file name=getopts_test.sh in the current working directory, one can produce output like

$ ./getopts_test.sh
$ ./getopts_test.sh -f
Non-option argument: '-f'
$ ./getopts_test.sh -h
usage: code/getopts_test.sh [-v] [--loglevel[=]<value>]
$ ./getopts_test.sh --help
$ ./getopts_test.sh -v
Parsing option: '-v'
$ ./getopts_test.sh --very-bad
$ ./getopts_test.sh --loglevel
Parsing option: '--loglevel', value: ''
$ ./getopts_test.sh --loglevel 11
Parsing option: '--loglevel', value: '11'
$ ./getopts_test.sh --loglevel=11
Parsing option: '--loglevel', value: '11'

Obviously getopts neither performs OPTERR checking nor option-argument parsing for the long options. The script fragment above shows how this may be done manually. The basic principle also works in the Debian Almquist shell ("dash"). Note the special case:

getopts -- "-:"  ## without the option terminator "-- " bash complains about "-:"
getopts "-:"     ## this works in the Debian Almquist shell ("dash")

Note that, as GreyCat from over at http://mywiki.wooledge.org/BashFAQ points out, this trick exploits a non-standard behaviour of the shell which permits the option-argument (i.e. the filename in "-f filename") to be concatenated to the option (as in "-ffilename"). The POSIX standard says there must be a space between them, which in the case of "-- longoption" would terminate the option-parsing and turn all longoptions into non-option arguments.

---

The built-in getopts command is still, AFAIK, limited to single-character options only.

There is (or used to be) an external program getopt that would reorganize a set of options such that it was easier to parse. You could adapt that design to handle long options too. Example usage:

aflag=no
bflag=no
flist=""
set -- $(getopt abf: "$@")
while [ $# -gt 0 ]
do
    case "$1" in
    (-a) aflag=yes;;
    (-b) bflag=yes;;
    (-f) flist="$flist $2"; shift;;
    (--) shift; break;;
    (-*) echo "$0: error - unrecognized option $1" 1>&2; exit 1;;
    (*)  break;;
    esac
    shift
done

# Process remaining non-option arguments
...

You could use a similar scheme with a getoptlong command.

Note that the fundamental weakness with the external getopt program is the difficulty of handling arguments with spaces in them, and in preserving those spaces accurately. This is why the built-in getopts is superior, albeit limited by the fact it only handles single-letter options.

---

Long options can be parsed by the standard getopts builtin as “arguments” to the - “option”

This is portable and native POSIX shell – no external programs or bashisms are needed.

This guide implements long options as arguments to the - option, so --alpha is seen by getopts as - with argument alpha and --bravo=foo is seen as - with argument bravo=foo. The true argument is harvested via shell parameter expansion, updating $OPT and $OPTARG.

In this example, -b and -c (and their long forms, --bravo and --charlie) have mandatory arguments. Arguments to long options come after equals signs, e.g. --bravo=foo (space delimiters for long options would be hard to implement, see below).

Because this uses the getopts builtin, this solution supports usage like cmd --bravo=foo -ac FILE (which has combined options -a and -c and interleaves long options with standard options) while most other answers here either struggle or fail to do that.

die() { echo "$*" >&2; exit 2; }  # complain to STDERR and exit with error
needs_arg() { if [ -z "$OPTARG" ]; then die "No arg for --$OPT option"; fi; }

while getopts ab:c:-: OPT; do
  # support long options: https://stackoverflow.com/a/28466267/519360
  if [ "$OPT" = "-" ]; then   # long option: reformulate OPT and OPTARG
    OPT="${OPTARG%%=*}"       # extract long option name
    OPTARG="${OPTARG#$OPT}"   # extract long option argument (may be empty)
    OPTARG="${OPTARG#=}"      # if long option argument, remove assigning `=`
  fi
  case "$OPT" in
    a | alpha )    alpha=true ;;
    b | bravo )    needs_arg; bravo="$OPTARG" ;;
    c | charlie )  needs_arg; charlie="$OPTARG" ;;
    ??* )          die "Illegal option --$OPT" ;;  # bad long option
    ? )            exit 2 ;;  # bad short option (error reported via getopts)
  esac
done
shift $((OPTIND-1)) # remove parsed options and args from $@ list

When the option is a dash (-), it is a long option. getopts will have parsed the actual long option into $OPTARG, e.g. --bravo=foo originally sets OPT='-' and OPTARG='bravo=foo'. The if stanza sets $OPT to the contents of $OPTARG before the first equals sign (bravo in our example) and then removes that from the beginning of $OPTARG (yielding =foo in this step, or an empty string if there is no =). Finally, we strip the argument's leading =. At this point, $OPT is either a short option (one character) or a long option (2+ characters).

The case then matches either short or long options. For short options, getopts automatically complains about options and missing arguments, so we have to replicate those manually using the needs_arg function, which fatally exits when $OPTARG is empty. The ??* condition will match any remaining long option (? matches a single character and * matches zero or more, so ??* matches 2+ characters), allowing us to issue the "Illegal option" error before exiting.

Minor bug: If somebody gives an invalid single-character long option (and it's not also a short option), this will exit with an error but without a message (this implementation assumes it's a short option). You could track that with an extra variable in the conditional preceding the case and then test for it in the final case condition, but I consider that too much of a corner case to bother.

Uppercase variable names: Generally, the advice is to reserve all-uppercase variables for system use. I'm keeping $OPT as all-uppercase to keep it in line with $OPTARG, but this does break that convention. I think it fits because this is something the system should have done, and it should be safe; I haven't heard of any standards that use this variable name.

To complain about unexpected arguments to long options: Mimic needs_arg with a flipped test to complain about an argument when one isn't expected:

no_arg() { if [ -n "$OPTARG" ]; then die "No arg allowed for --$OPT option"; fi; }

To accept long options with space-delimited arguments: You can pull in the next argument with eval "ARG_B=\"\$$OPTIND\"" (or with bash's indirect expansion, ARG_B="${!OPTIND}") and then increment $OPTIND as noted in an older version of this answer, but it's unreliable; getopts can prematurely terminate on the assumption that the argument was beyond its scope and some implementations don't take well to manual manipulations of $OPTIND.

---

Here's an example that actually uses getopt with long options:

aflag=no
bflag=no
cargument=none

# options may be followed by one colon to indicate they have a required argument
if ! options=$(getopt -o abc: -l along,blong,clong: -- "$@")
then
    # something went wrong, getopt will put out an error message for us
    exit 1
fi

set -- $options

while [ $# -gt 0 ]
do
    case $1 in
    -a|--along) aflag="yes" ;;
    -b|--blong) bflag="yes" ;;
    # for options with required arguments, an additional shift is required
    -c|--clong) cargument="$2" ; shift;;
    (--) shift; break;;
    (-*) echo "$0: error - unrecognized option $1" 1>&2; exit 1;;
    (*) break;;
    esac
    shift
done

---

Using getopts with short/long options and arguments

Works with all combinations, e.g:

foobar -f --bar

foobar --foo -b

foobar -bf --bar --foobar

foobar -fbFBAshorty --bar -FB --arguments=longhorn

foobar -fA "text shorty" -B --arguments="text longhorn"

bash foobar -F --barfoo

sh foobar -B --foobar - ...

bash ./foobar -F --bar

Some declarations for this example

Options=$@
Optnum=$#
sfoo='no '
sbar='no '
sfoobar='no '
sbarfoo='no '
sarguments='no '
sARG=empty
lfoo='no '
lbar='no '
lfoobar='no '
lbarfoo='no '
larguments='no '
lARG=empty

How the Usage function would look

function _usage() 
{
  ###### U S A G E : Help and ERROR ######
  cat <<EOF
   foobar $Options
  $*
          Usage: foobar <[options]>
          Options:
                  -b   --bar            Set bar to yes    ($foo)
                  -f   --foo            Set foo to yes    ($bart)
                  -h   --help           Show this message
                  -A   --arguments=...  Set arguments to yes ($arguments) AND get ARGUMENT ($ARG)
                  -B   --barfoo         Set barfoo to yes ($barfoo)
                  -F   --foobar         Set foobar to yes ($foobar)
EOF
}

[ $# = 0 ] && _usage "  >>>>>>>> no options given "

getops with long/short flags as well as long arguments

while getopts ':bfh-A:BF' OPTION ; do
  case "$OPTION" in
    b  ) sbar=yes                       ;;
    f  ) sfoo=yes                       ;;
    h  ) _usage                         ;;   
    A  ) sarguments=yes;sARG="$OPTARG"  ;;
    B  ) sbarfoo=yes                    ;;
    F  ) sfoobar=yes                    ;;
    -  ) [ $OPTIND -ge 1 ] && optind=$(expr $OPTIND - 1 ) || optind=$OPTIND
         eval OPTION="\$$optind"
         OPTARG=$(echo $OPTION | cut -d'=' -f2)
         OPTION=$(echo $OPTION | cut -d'=' -f1)
         case $OPTION in
             --foo       ) lfoo=yes                       ;;
             --bar       ) lbar=yes                       ;;
             --foobar    ) lfoobar=yes                    ;;
             --barfoo    ) lbarfoo=yes                    ;;
             --help      ) _usage                         ;;
             --arguments ) larguments=yes;lARG="$OPTARG"  ;; 
             * )  _usage " Long: >>>>>>>> invalid options (long) " ;;
         esac
       OPTIND=1
       shift
      ;;
    ? )  _usage "Short: >>>>>>>> invalid options (short) "  ;;
  esac
done

Output

##################################################################
echo "----------------------------------------------------------"
echo "RESULT short-foo      : $sfoo                                    long-foo      : $lfoo"
echo "RESULT short-bar      : $sbar                                    long-bar      : $lbar"
echo "RESULT short-foobar   : $sfoobar                                 long-foobar   : $lfoobar"
echo "RESULT short-barfoo   : $sbarfoo                                 long-barfoo   : $lbarfoo"
echo "RESULT short-arguments: $sarguments  with Argument = \"$sARG\"   long-arguments: $larguments and $lARG"

Combining the above into a cohesive script

#!/bin/bash
# foobar: getopts with short and long options AND arguments

function _cleanup ()
{
  unset -f _usage _cleanup ; return 0
}

## Clear out nested functions on exit
trap _cleanup INT EXIT RETURN

###### some declarations for this example ######
Options=$@
Optnum=$#
sfoo='no '
sbar='no '
sfoobar='no '
sbarfoo='no '
sarguments='no '
sARG=empty
lfoo='no '
lbar='no '
lfoobar='no '
lbarfoo='no '
larguments='no '
lARG=empty

function _usage() 
{
  ###### U S A G E : Help and ERROR ######
  cat <<EOF
   foobar $Options
   $*
          Usage: foobar <[options]>
          Options:
                  -b   --bar            Set bar to yes    ($foo)
                    -f   --foo            Set foo to yes    ($bart)
                      -h   --help           Show this message
                  -A   --arguments=...  Set arguments to yes ($arguments) AND get ARGUMENT ($ARG)
                  -B   --barfoo         Set barfoo to yes ($barfoo)
                  -F   --foobar         Set foobar to yes ($foobar)
EOF
}

[ $# = 0 ] && _usage "  >>>>>>>> no options given "

##################################################################    
#######  "getopts" with: short options  AND  long options  #######
#######            AND  short/long arguments               #######
while getopts ':bfh-A:BF' OPTION ; do
  case "$OPTION" in
    b  ) sbar=yes                       ;;
    f  ) sfoo=yes                       ;;
    h  ) _usage                         ;;   
    A  ) sarguments=yes;sARG="$OPTARG"  ;;
    B  ) sbarfoo=yes                    ;;
    F  ) sfoobar=yes                    ;;
    -  ) [ $OPTIND -ge 1 ] && optind=$(expr $OPTIND - 1 ) || optind=$OPTIND
         eval OPTION="\$$optind"
         OPTARG=$(echo $OPTION | cut -d'=' -f2)
         OPTION=$(echo $OPTION | cut -d'=' -f1)
         case $OPTION in
             --foo       ) lfoo=yes                       ;;
             --bar       ) lbar=yes                       ;;
             --foobar    ) lfoobar=yes                    ;;
             --barfoo    ) lbarfoo=yes                    ;;
             --help      ) _usage                         ;;
               --arguments ) larguments=yes;lARG="$OPTARG"  ;; 
             * )  _usage " Long: >>>>>>>> invalid options (long) " ;;
         esac
       OPTIND=1
       shift
      ;;
    ? )  _usage "Short: >>>>>>>> invalid options (short) "  ;;
  esac
done

---

Take a look at shFlags which is a portable shell library (meaning: sh, bash, dash, ksh, zsh on Linux, Solaris, etc.).

It makes adding new flags as simple as adding one line to your script, and it provides an auto generated usage function.

Here is a simple Hello, world! using shFlag:

#!/bin/sh

# source shflags from current directory
. ./shflags

# define a 'name' command-line string flag
DEFINE_string 'name' 'world' 'name to say hello to' 'n'

# parse the command-line
FLAGS "$@" || exit 1
eval set -- "${FLAGS_ARGV}"

# say hello
echo "Hello, ${FLAGS_name}!"

For OSes that have the enhanced getopt that supports long options (e.g. Linux), you can do:

$ ./hello_world.sh --name Kate
Hello, Kate!

For the rest, you must use the short option:

$ ./hello_world.sh -n Kate
Hello, Kate!

Adding a new flag is as simple as adding a new DEFINE_ call.

---

Another way...

# translate long options to short
for arg
do
    delim=""
    case "$arg" in
       --help) args="${args}-h ";;
       --verbose) args="${args}-v ";;
       --config) args="${args}-c ";;
       # pass through anything else
       *) [[ "${arg:0:1}" == "-" ]] || delim="\""
           args="${args}${delim}${arg}${delim} ";;
    esac
done
# reset the translated args
eval set -- $args
# now we can process with getopt
while getopts ":hvc:" opt; do
    case $opt in
        h)  usage ;;
        v)  VERBOSE=true ;;
        c)  source $OPTARG ;;
        \?) usage ;;
        :)
        echo "option -$OPTARG requires an argument"
        usage
        ;;
    esac
done

---

I kind of solved this way:

# A string with command options
options=$@

# An array with all the arguments
arguments=($options)

# Loop index
index=0

for argument in $options
  do
    # Incrementing index
    index=`expr $index + 1`

    # The conditions
    case $argument in
      -a) echo "key $argument value ${arguments[index]}" ;;
      -abc) echo "key $argument value ${arguments[index]}" ;;
    esac
  done

exit;

Am I being dumb or something? getopt and getopts are so confusing.

---

In case you don't want the getopt dependency, you can do this:

while test $# -gt 0
do
  case $1 in

  # Normal option processing
    -h | --help)
      # usage and help
      ;;
    -v | --version)
      # version info
      ;;
  # ...

  # Special cases
    --)
      break
      ;;
    --*)
      # error unknown (long) option $1
      ;;
    -?)
      # error unknown (short) option $1
      ;;

  # FUN STUFF HERE:
  # Split apart combined short options
    -*)
      split=$1
      shift
      set -- $(echo "$split" | cut -c 2- | sed 's/./-& /g') "$@"
      continue
      ;;

  # Done with options
    *)
      break
      ;;
  esac

  # for testing purposes:
  echo "$1"

  shift
done

Of course, then you can't use long style options with one dash. And if you want to add shortened versions (e.g. --verbos instead of --verbose), then you need to add those manually.

But if you are looking to get getopts functionality along with long options, this is a simple way to do it.

I also put this snippet in a gist.

---

The built-in getopts can't do this. There is an external getopt(1) program that can do this, but you only get it on Linux from the util-linux package. It comes with an example script getopt-parse.bash.

There is also a getopts_long written as a shell function.

---

#!/bin/bash
while getopts "abc:d:" flag
do
  case $flag in
    a) echo "[getopts:$OPTIND]==> -$flag";;
    b) echo "[getopts:$OPTIND]==> -$flag";;
    c) echo "[getopts:$OPTIND]==> -$flag $OPTARG";;
    d) echo "[getopts:$OPTIND]==> -$flag $OPTARG";;
  esac
done

shift $((OPTIND-1))
echo "[otheropts]==> $@"

exit

.

#!/bin/bash
until [ -z "$1" ]; do
  case $1 in
    "--dlong")
      shift
      if [ "${1:1:0}" != "-" ]
      then
        echo "==> dlong $1"
        shift
      fi;;
    *) echo "==> other $1"; shift;;
  esac
done
exit

---

In ksh93, getopts does support long names...

while getopts "f(file):s(server):" flag
do
    echo "$flag" $OPTIND $OPTARG
done

Or so the tutorials I have found have said. Try it and see.

---

Inventing yet another version of the wheel...

This function is a (hopefully) POSIX-compatible plain bourne shell replacement for GNU getopt. It supports short/long options which can accept mandatory/optional/no arguments, and the way in which options are specified is almost identical to GNU getopt, so conversion is trivial.

Of course this is still a sizeable chunk of code to drop into a script, but it's about half the lines of the well-known getopt_long shell function, and might be preferable in cases where you just want to replace existing GNU getopt uses.

This is pretty new code, so YMMV (and definitely please let me know if this isn't actually POSIX-compatible for any reason -- portability was the intention from the outset, but I don't have a useful POSIX test environment).

Code and example usage follows:

#!/bin/sh
# posix_getopt shell function
# Author: Phil S.
# Version: 1.0
# Created: 2016-07-05
# URL: http://stackoverflow.com/a/37087374/324105

# POSIX-compatible argument quoting and parameter save/restore
# http://www.etalabs.net/sh_tricks.html
# Usage:
# parameters=$(save "$@") # save the original parameters.
# eval "set -- ${parameters}" # restore the saved parameters.
save () {
    local param
    for param; do
        printf %s\\n "$param" \
            | sed "s/'/'\\\\''/g;1s/^/'/;\$s/\$/' \\\\/"
    done
    printf %s\\n " "
}

# Exit with status $1 after displaying error message $2.
exiterr () {
    printf %s\\n "$2" >&2
    exit $1
}

# POSIX-compatible command line option parsing.
# This function supports long options and optional arguments, and is
# a (largely-compatible) drop-in replacement for GNU getopt.
#
# Instead of:
# opts=$(getopt -o "$shortopts" -l "$longopts" -- "$@")
# eval set -- ${opts}
#
# We instead use:
# opts=$(posix_getopt "$shortopts" "$longopts" "$@")
# eval "set -- ${opts}"
posix_getopt () { # args: "$shortopts" "$longopts" "$@"
    local shortopts longopts \
          arg argtype getopt nonopt opt optchar optword suffix

    shortopts="$1"
    longopts="$2"
    shift 2

    getopt=
    nonopt=
    while [ $# -gt 0 ]; do
        opt=
        arg=
        argtype=
        case "$1" in
            # '--' means don't parse the remaining options
            ( -- ) {
                getopt="${getopt}$(save "$@")"
                shift $#
                break
            };;
            # process short option
            ( -[!-]* ) {         # -x[foo]
                suffix=${1#-?}   # foo
                opt=${1%$suffix} # -x
                optchar=${opt#-} # x
                case "${shortopts}" in
                    ( *${optchar}::* ) { # optional argument
                        argtype=optional
                        arg="${suffix}"
                        shift
                    };;
                    ( *${optchar}:* ) { # required argument
                        argtype=required
                        if [ -n "${suffix}" ]; then
                            arg="${suffix}"
                            shift
                        else
                            case "$2" in
                                ( -* ) exiterr 1 "$1 requires an argument";;
                                ( ?* ) arg="$2"; shift 2;;
                                (  * ) exiterr 1 "$1 requires an argument";;
                            esac
                        fi
                    };;
                    ( *${optchar}* ) { # no argument
                        argtype=none
                        arg=
                        shift
                        # Handle multiple no-argument parameters combined as
                        # -xyz instead of -x -y -z. If we have just shifted
                        # parameter -xyz, we now replace it with -yz (which
                        # will be processed in the next iteration).
                        if [ -n "${suffix}" ]; then
                            eval "set -- $(save "-${suffix}")$(save "$@")"
                        fi
                    };;
                    ( * ) exiterr 1 "Unknown option $1";;
                esac
            };;
            # process long option
            ( --?* ) {            # --xarg[=foo]
                suffix=${1#*=}    # foo (unless there was no =)
                if [ "${suffix}" = "$1" ]; then
                    suffix=
                fi
                opt=${1%=$suffix} # --xarg
                optword=${opt#--} # xarg
                case ",${longopts}," in
                    ( *,${optword}::,* ) { # optional argument
                        argtype=optional
                        arg="${suffix}"
                        shift
                    };;
                    ( *,${optword}:,* ) { # required argument
                        argtype=required
                        if [ -n "${suffix}" ]; then
                            arg="${suffix}"
                            shift
                        else
                            case "$2" in
                                ( -* ) exiterr 1 \
                                       "--${optword} requires an argument";;
                                ( ?* ) arg="$2"; shift 2;;
                                (  * ) exiterr 1 \
                                       "--${optword} requires an argument";;
                            esac
                        fi
                    };;
                    ( *,${optword},* ) { # no argument
                        if [ -n "${suffix}" ]; then
                            exiterr 1 "--${optword} does not take an argument"
                        fi
                        argtype=none
                        arg=
                        shift
                    };;
                    ( * ) exiterr 1 "Unknown option $1";;
                esac
            };;
            # any other parameters starting with -
            ( -* ) exiterr 1 "Unknown option $1";;
            # remember non-option parameters
            ( * ) nonopt="${nonopt}$(save "$1")"; shift;;
        esac

        if [ -n "${opt}" ]; then
            getopt="${getopt}$(save "$opt")"
            case "${argtype}" in
                ( optional|required ) {
                    getopt="${getopt}$(save "$arg")"
                };;
            esac
        fi
    done

    # Generate function output, suitable for:
    # eval "set -- $(posix_getopt ...)"
    printf %s "${getopt}"
    if [ -n "${nonopt}" ]; then
        printf %s "$(save "--")${nonopt}"
    fi
}

Example usage:

# Process command line options
shortopts="hvd:c::s::L:D"
longopts="help,version,directory:,client::,server::,load:,delete"
#opts=$(getopt -o "$shortopts" -l "$longopts" -n "$(basename $0)" -- "$@")
opts=$(posix_getopt "$shortopts" "$longopts" "$@")
if [ $? -eq 0 ]; then
    #eval set -- ${opts}
    eval "set -- ${opts}"
    while [ $# -gt 0 ]; do
        case "$1" in
            ( --                ) shift; break;;
            ( -h|--help         ) help=1; shift; break;;
            ( -v|--version      ) version_help=1; shift; break;;
            ( -d|--directory    ) dir=$2; shift 2;;
            ( -c|--client       ) useclient=1; client=$2; shift 2;;
            ( -s|--server       ) startserver=1; server_name=$2; shift 2;;
            ( -L|--load         ) load=$2; shift 2;;
            ( -D|--delete       ) delete=1; shift;;
        esac
    done
else
    shorthelp=1 # getopt returned (and reported) an error.
fi

---

I only write shell scripts now and then and fall out of practice, so any feedback is appreciated.

Using the strategy proposed by @Arvid Requate, we noticed some user errors. A user who forgets to include a value will accidentally have the next option's name treated as a value:

./getopts_test.sh --loglevel= --toc=TRUE

will cause the value of "loglevel" to be seen as "--toc=TRUE". This can be avoided.

I adapted some ideas about checking user error for CLI from http://mwiki.wooledge.org/BashFAQ/035 discussion of manual parsing. I inserted error checking into handling both "-" and "--" arguments.

Then I started fiddling around with the syntax, so any errors in here are strictly my fault, not the original authors.

My approach helps users who prefer to enter long with or without the equal sign. That is, it should have same response to "--loglevel 9" as "--loglevel=9". In the --/space method, it is not possible to know for sure if the user forgets an argument, so some guessing is needed.

if the user has the long/equal sign format (--opt=), then a space after = triggers an error because an argument was not supplied. if user has long/space arguments (--opt ), this script causes a fail if no argument follows (end of command) or if argument begins with dash)

In case you are starting out on this, there is an interesting difference between "--opt=value" and "--opt value" formats. With the equal sign, the command line argument is seen as "opt=value" and the work to handle that is string parsing, to separate at the "=". In contrast, with "--opt value", the name of the argument is "opt" and we have the challenge of getting the next value supplied in the command line. That's where @Arvid Requate used ${!OPTIND}, the indirect reference. I still don't understand that, well, at all, and comments in BashFAQ seem to warn against that style (http://mywiki.wooledge.org/BashFAQ/006). BTW, I don't think previous poster's comments about importance of OPTIND=$(( $OPTIND + 1 )) are correct. I mean to say, I see no harm from omitting it.

In newest version of this script, flag -v means VERBOSE printout.

Save it in a file called "cli-5.sh", make executable, and any of these will work, or fail in the desired way

./cli-5.sh  -v --loglevel=44 --toc  TRUE
./cli-5.sh  -v --loglevel=44 --toc=TRUE
./cli-5.sh --loglevel 7
./cli-5.sh --loglevel=8
./cli-5.sh -l9

./cli-5.sh  --toc FALSE --loglevel=77
./cli-5.sh  --toc=FALSE --loglevel=77

./cli-5.sh   -l99 -t yyy
./cli-5.sh   -l 99 -t yyy

Here is example output of the error-checking on user intpu

$ ./cli-5.sh  --toc --loglevel=77
ERROR: toc value must not have dash at beginning
$ ./cli-5.sh  --toc= --loglevel=77
ERROR: value for toc undefined

You should consider turning on -v, because it prints out internals of OPTIND and OPTARG

#/usr/bin/env bash

## Paul Johnson
## 20171016
##

## Combines ideas from
## https://stackoverflow.com/questions/402377/using-getopts-in-bash-shell-script-to-get-long-and-short-command-line-options
## by @Arvid Requate, and http://mwiki.wooledge.org/BashFAQ/035

# What I don't understand yet: 
# In @Arvid REquate's answer, we have 
# val="${!OPTIND}"; OPTIND=$(( $OPTIND + 1 ))
# this works, but I don't understand it!


die() {
    printf '%s\n' "$1" >&2
    exit 1
}

printparse(){
    if [ ${VERBOSE} -gt 0 ]; then
        printf 'Parse: %s%s%s\n' "$1" "$2" "$3" >&2;
    fi
}

showme(){
    if [ ${VERBOSE} -gt 0 ]; then
        printf 'VERBOSE: %s\n' "$1" >&2;
    fi
}


VERBOSE=0
loglevel=0
toc="TRUE"

optspec=":vhl:t:-:"
while getopts "$optspec" OPTCHAR; do

    showme "OPTARG:  ${OPTARG[*]}"
    showme "OPTIND:  ${OPTIND[*]}"
    case "${OPTCHAR}" in
        -)
            case "${OPTARG}" in
                loglevel) #argument has no equal sign
                    opt=${OPTARG}
                    val="${!OPTIND}"
                    ## check value. If negative, assume user forgot value
                    showme "OPTIND is {$OPTIND} {!OPTIND} has value \"${!OPTIND}\""
                    if [[ "$val" == -* ]]; then
                        die "ERROR: $opt value must not have dash at beginning"
                    fi
                    ## OPTIND=$(( $OPTIND + 1 )) # CAUTION! no effect?
                    printparse "--${OPTARG}" "  " "${val}"
                    loglevel="${val}"
                    shift
                    ;;
                loglevel=*) #argument has equal sign
                    opt=${OPTARG%=*}
                    val=${OPTARG#*=}
                    if [ "${OPTARG#*=}" ]; then
                        printparse "--${opt}" "=" "${val}"
                        loglevel="${val}"
                        ## shift CAUTION don't shift this, fails othewise
                    else
                        die "ERROR: $opt value must be supplied"
                    fi
                    ;;
                toc) #argument has no equal sign
                    opt=${OPTARG}
                    val="${!OPTIND}"
                    ## check value. If negative, assume user forgot value
                    showme "OPTIND is {$OPTIND} {!OPTIND} has value \"${!OPTIND}\""
                    if [[ "$val" == -* ]]; then
                        die "ERROR: $opt value must not have dash at beginning"
                    fi
                    ## OPTIND=$(( $OPTIND + 1 )) #??
                    printparse "--${opt}" " " "${val}"
                    toc="${val}"
                    shift
                    ;;
                toc=*) #argument has equal sign
                    opt=${OPTARG%=*}
                    val=${OPTARG#*=}
                    if [ "${OPTARG#*=}" ]; then
                        toc=${val}
                        printparse "--$opt" " -> " "$toc"
                        ##shift ## NO! dont shift this
                    else
                        die "ERROR: value for $opt undefined"
                    fi
                    ;;

                help)
                    echo "usage: $0 [-v] [--loglevel[=]<value>] [--toc[=]<TRUE,FALSE>]" >&2
                    exit 2
                    ;;
                *)
                    if [ "$OPTERR" = 1 ] && [ "${optspec:0:1}" != ":" ]; then
                        echo "Unknown option --${OPTARG}" >&2
                    fi
                    ;;
            esac;;
        h|-\?|--help)
            ## must rewrite this for all of the arguments
            echo "usage: $0 [-v] [--loglevel[=]<value>] [--toc[=]<TRUE,FALSE>]" >&2
            exit 2
            ;;
        l)
            loglevel=${OPTARG}
            printparse "-l" " "  "${loglevel}"
            ;;
        t)
            toc=${OPTARG}
            ;;
        v)
            VERBOSE=1
            ;;

        *)
            if [ "$OPTERR" != 1 ] || [ "${optspec:0:1}" = ":" ]; then
                echo "Non-option argument: '-${OPTARG}'" >&2
            fi
            ;;
    esac
done



echo "
After Parsing values
"
echo "loglevel  $loglevel" 
echo "toc  $toc"

---

The accepted answer does a very nice job of pointing out all the shortcomings of bash built-in getopts. The answer ends with:

So while it is possible to write more code to work around the lack of support for long options, this is a lot more work and partially defeats the purpose of using a getopt parser to simplify your code.

And even though I agree in principle with that statement, I feel that the number of times we all implemented this feature in various scripts justifies putting a bit of effort into creating a "standardised", well tested solution.

As such, I've "upgraded" bash built in getopts by implementing getopts_long in pure bash, with no external dependencies. The usage of the function is 100% compatible with the built-in getopts.

By including getopts_long (which is hosted on GitHub) in a script, the answer to the original question can be implemented as simply as:

source "${PATH_TO}/getopts_long.bash"

while getopts_long ':c: copyfile:' OPTKEY; do
    case ${OPTKEY} in
        'c'|'copyfile')
            echo 'file supplied -- ${OPTARG}'
            ;;
        '?')
            echo "INVALID OPTION -- ${OPTARG}" >&2
            exit 1
            ;;
        ':')
            echo "MISSING ARGUMENT for option -- ${OPTARG}" >&2
            exit 1
            ;;
        *)
            echo "Misconfigured OPTSPEC or uncaught option -- ${OPTKEY}" >&2
            exit 1
            ;;
    esac
done

shift $(( OPTIND - 1 ))
[[ "${1}" == "--" ]] && shift

---

I don't have enough rep yet to comment or vote his solution up, but sme's answer worked extremely well for me. The only issue I ran into was that the arguments end up wrapped in single-quotes (so I have an strip them out).

I also added some example usages and HELP text. I'll included my slightly extended version here:

#!/bin/bash

# getopt example
# from: https://stackoverflow.com/questions/402377/using-getopts-in-bash-shell-script-to-get-long-and-short-command-line-options
HELP_TEXT=\
"   USAGE:\n
    Accepts - and -- flags, can specify options that require a value, and can be in any order. A double-hyphen (--) will stop processing options.\n\n

    Accepts the following forms:\n\n

    getopt-example.sh -a -b -c value-for-c some-arg\n
    getopt-example.sh -c value-for-c -a -b some-arg\n
    getopt-example.sh -abc some-arg\n
    getopt-example.sh --along --blong --clong value-for-c -a -b -c some-arg\n
    getopt-example.sh some-arg --clong value-for-c\n
    getopt-example.sh
"

aflag=false
bflag=false
cargument=""

# options may be followed by one colon to indicate they have a required argument
if ! options=$(getopt -o abc:h\? -l along,blong,help,clong: -- "$@")
then
    # something went wrong, getopt will put out an error message for us
    exit 1
fi

set -- $options

while [ $# -gt 0 ]
do
    case $1 in
    -a|--along) aflag=true ;;
    -b|--blong) bflag=true ;;
    # for options with required arguments, an additional shift is required
    -c|--clong) cargument="$2" ; shift;;
    -h|--help|-\?) echo -e $HELP_TEXT; exit;;
    (--) shift; break;;
    (-*) echo "$0: error - unrecognized option $1" 1>&2; exit 1;;
    (*) break;;
    esac
    shift
done

# to remove the single quotes around arguments, pipe the output into:
# | sed -e "s/^'\\|'$//g"  (just leading/trailing) or | sed -e "s/'//g"  (all)

echo aflag=${aflag}
echo bflag=${bflag}
echo cargument=${cargument}

while [ $# -gt 0 ]
do
    echo arg=$1
    shift

    if [[ $aflag == true ]]; then
        echo a is true
    fi

done

---

Here you can find a few different approaches for complex option parsing in bash: http://mywiki.wooledge.org/ComplexOptionParsing

I did create the following one, and I think it's a good one, because it's minimal code and both long and short options work. A long option can also have multiple arguments with this approach.

#!/bin/bash
# Uses bash extensions.  Not portable as written.

declare -A longoptspec
longoptspec=( [loglevel]=1 ) #use associative array to declare how many arguments a long option expects, in this case we declare that loglevel expects/has one argument, long options that aren't listed i n this way will have zero arguments by default
optspec=":h-:"
while getopts "$optspec" opt; do
while true; do
    case "${opt}" in
        -) #OPTARG is name-of-long-option or name-of-long-option=value
            if [[ "${OPTARG}" =~ .*=.* ]] #with this --key=value format only one argument is possible
            then
                opt=${OPTARG/=*/}
                OPTARG=${OPTARG#*=}
                ((OPTIND--))    
            else #with this --key value1 value2 format multiple arguments are possible
                opt="$OPTARG"
                OPTARG=(${@:OPTIND:$((longoptspec[$opt]))})
            fi
            ((OPTIND+=longoptspec[$opt]))
            continue #now that opt/OPTARG are set we can process them as if getopts would've given us long options
            ;;
        loglevel)
          loglevel=$OPTARG
            ;;
        h|help)
            echo "usage: $0 [--loglevel[=]<value>]" >&2
            exit 2
            ;;
    esac
break; done
done

# End of file

---

I have been working on that subject for quite a long time... and made my own library which you will need to source in your main script. See libopt4shell and cd2mpc for an example. Hope it helps !

---

An improved solution:

# translate long options to short
# Note: This enable long options but disable "--?*" in $OPTARG, or disable long options after  "--" in option fields.
for ((i=1;$#;i++)) ; do
    case "$1" in
        --)
            # [ ${args[$((i-1))]} == ... ] || EndOpt=1 ;;& # DIRTY: we still can handle some execptions...
            EndOpt=1 ;;&
        --version) ((EndOpt)) && args[$i]="$1"  || args[$i]="-V";;
        # default case : short option use the first char of the long option:
        --?*) ((EndOpt)) && args[$i]="$1"  || args[$i]="-${1:2:1}";;
        # pass through anything else:
        *) args[$i]="$1" ;;
    esac
    shift
done
# reset the translated args
set -- "${args[@]}"

function usage {
echo "Usage: $0 [options] files" >&2
    exit $1
}

# now we can process with getopt
while getopts ":hvVc:" opt; do
    case $opt in
        h)  usage ;;
        v)  VERBOSE=true ;;
        V)  echo $Version ; exit ;;
        c)  source $OPTARG ;;
        \?) echo "unrecognized option: -$opt" ; usage -1 ;;
        :)
        echo "option -$OPTARG requires an argument"
        usage -1
        ;;
    esac
done

shift $((OPTIND-1))
[[ "$1" == "--" ]] && shift

---

Maybe it's simpler to use ksh, just for the getopts part, if need long command line options, as it can be easier done there.

# Working Getopts Long => KSH

#! /bin/ksh
# Getopts Long
USAGE="s(showconfig)"
USAGE+="c:(createdb)"
USAGE+="l:(createlistener)"
USAGE+="g:(generatescripts)"
USAGE+="r:(removedb)"
USAGE+="x:(removelistener)"
USAGE+="t:(createtemplate)"
USAGE+="h(help)"

while getopts "$USAGE" optchar ; do
    case $optchar in
    s)  echo "Displaying Configuration" ;;
        c)  echo "Creating Database $OPTARG" ;;
    l)  echo "Creating Listener LISTENER_$OPTARG" ;;
    g)  echo "Generating Scripts for Database $OPTARG" ;;
    r)  echo "Removing Database $OPTARG" ;;
    x)  echo "Removing Listener LISTENER_$OPTARG" ;;
    t)  echo "Creating Database Template" ;;
    h)  echo "Help" ;;
    esac
done

---

I wanted something without external dependencies, with strict bash support (-u), and I needed it to work on even the older bash versions. This handles various types of params:

short bools (-h)

short options (-i "image.jpg")

long bools (--help)

equals options (--file="filename.ext")

space options (--file "filename.ext")

concatinated bools (-hvm)

Just insert the following at the top of your script:

# Check if a list of params contains a specific param
# usage: if _param_variant "h|?|help p|path f|file long-thing t|test-thing" "file" ; then ...
# the global variable $key is updated to the long notation (last entry in the pipe delineated list, if applicable)
_param_variant() {
  for param in $1 ; do
    local variants=${param//\|/ }
    for variant in $variants ; do
      if [[ "$variant" = "$2" ]] ; then
        # Update the key to match the long version
        local arr=(${param//\|/ })
        let last=${#arr[@]}-1
        key="${arr[$last]}"
        return 0
      fi
    done
  done
  return 1
}

# Get input parameters in short or long notation, with no dependencies beyond bash
# usage:
#     # First, set your defaults
#     param_help=false
#     param_path="."
#     param_file=false
#     param_image=false
#     param_image_lossy=true
#     # Define allowed parameters
#     allowed_params="h|?|help p|path f|file i|image image-lossy"
#     # Get parameters from the arguments provided
#     _get_params $*
#
# Parameters will be converted into safe variable names like:
#     param_help,
#     param_path,
#     param_file,
#     param_image,
#     param_image_lossy
#
# Parameters without a value like "-h" or "--help" will be treated as
# boolean, and will be set as param_help=true
#
# Parameters can accept values in the various typical ways:
#     -i "path/goes/here"
#     --image "path/goes/here"
#     --image="path/goes/here"
#     --image=path/goes/here
# These would all result in effectively the same thing:
#     param_image="path/goes/here"
#
# Concatinated short parameters (boolean) are also supported
#     -vhm is the same as -v -h -m
_get_params(){

  local param_pair
  local key
  local value
  local shift_count

  while : ; do
    # Ensure we have a valid param. Allows this to work even in -u mode.
    if [[ $# == 0 || -z $1 ]] ; then
      break
    fi

    # Split the argument if it contains "="
    param_pair=(${1//=/ })
    # Remove preceeding dashes
    key="${param_pair[0]#--}"

    # Check for concatinated boolean short parameters.
    local nodash="${key#-}"
    local breakout=false
    if [[ "$nodash" != "$key" && ${#nodash} -gt 1 ]]; then
      # Extrapolate multiple boolean keys in single dash notation. ie. "-vmh" should translate to: "-v -m -h"
      local short_param_count=${#nodash}
      let new_arg_count=$#+$short_param_count-1
      local new_args=""
      # $str_pos is the current position in the short param string $nodash
      for (( str_pos=0; str_pos<new_arg_count; str_pos++ )); do
        # The first character becomes the current key
        if [ $str_pos -eq 0 ] ; then
          key="${nodash:$str_pos:1}"
          breakout=true
        fi
        # $arg_pos is the current position in the constructed arguments list
        let arg_pos=$str_pos+1
        if [ $arg_pos -gt $short_param_count ] ; then
          # handle other arguments
          let orignal_arg_number=$arg_pos-$short_param_count+1
          local new_arg="${!orignal_arg_number}"
        else
          # break out our one argument into new ones
          local new_arg="-${nodash:$str_pos:1}"
        fi
        new_args="$new_args \"$new_arg\""
      done
      # remove the preceding space and set the new arguments
      eval set -- "${new_args# }"
    fi
    if ! $breakout ; then
      key="$nodash"
    fi

    # By default we expect to shift one argument at a time
    shift_count=1
    if [ "${#param_pair[@]}" -gt "1" ] ; then
      # This is a param with equals notation
      value="${param_pair[1]}"
    else
      # This is either a boolean param and there is no value,
      # or the value is the next command line argument
      # Assume the value is a boolean true, unless the next argument is found to be a value.
      value=true
      if [[ $# -gt 1 && -n "$2" ]]; then
        local nodash="${2#-}"
        if [ "$nodash" = "$2" ]; then
          # The next argument has NO preceding dash so it is a value
          value="$2"
          shift_count=2
        fi
      fi
    fi

    # Check that the param being passed is one of the allowed params
    if _param_variant "$allowed_params" "$key" ; then
      # --key-name will now become param_key_name
      eval param_${key//-/_}="$value"
    else
      printf 'WARNING: Unknown option (ignored): %s\n' "$1" >&2
    fi
    shift $shift_count
  done
}

And use it like so:

# Assign defaults for parameters
param_help=false
param_path=$(pwd)
param_file=false
param_image=true
param_image_lossy=true
param_image_lossy_quality=85

# Define the params we will allow
allowed_params="h|?|help p|path f|file i|image image-lossy image-lossy-quality"

# Get the params from arguments provided
_get_params $*

---

if simply this is how you want to call the script

myscript.sh --input1 "ABC" --input2 "PQR" --input2 "XYZ"

then you can follow this simplest way to achieve it with the help of getopt and --longoptions

try this , hope this is useful

# Read command line options
ARGUMENT_LIST=(
    "input1"
    "input2"
    "input3"
)



# read arguments
opts=$(getopt \
    --longoptions "$(printf "%s:," "${ARGUMENT_LIST[@]}")" \
    --name "$(basename "$0")" \
    --options "" \
    -- "$@"
)


echo $opts

eval set --$opts

while true; do
    case "$1" in
    --input1)  
        shift
        empId=$1
        ;;
    --input2)  
        shift
        fromDate=$1
        ;;
    --input3)  
        shift
        toDate=$1
        ;;
      --)
        shift
        break
        ;;
    esac
    shift
done

---

getopts "could be used" for parsing long options as long as you don't expect them to have arguments...

Here's how to:

$ cat > longopt
while getopts 'e:-:' OPT; do
  case $OPT in
    e) echo echo: $OPTARG;;
    -) #long option
       case $OPTARG in
         long-option) echo long option;;
         *) echo long option: $OPTARG;;
       esac;;
  esac
done

$ bash longopt -e asd --long-option --long1 --long2 -e test
echo: asd
long option
long option: long1
long option: long2
echo: test

If you try to use OPTIND for getting a parameter for the long option, getopts will treat it as the first no optional positional parameter and will stop parsing any other parameters. In such a case you'll be better off handling it manually with a simple case statement.

This will "always" work:

$ cat >longopt2
while (($#)); do
    OPT=$1
    shift
    case $OPT in
        --*) case ${OPT:2} in
            long1) echo long1 option;;
            complex) echo comples with argument $1; shift;;
        esac;;

        -*) case ${OPT:1} in
            a) echo short option a;;
            b) echo short option b with parameter $1; shift;;
        esac;;
    esac
done


$ bash longopt2 --complex abc -a --long -b test
comples with argument abc
short option a
short option b with parameter test

Albeit is not as flexible as getopts and you have to do much of the error checking code yourself within the case instances...

But it is an option.

---

In order to stay cross-platform compatible, and avoid the reliance on external executables, I ported some code from another language.

I find it very easy to use, here is an example:

ArgParser::addArg "[h]elp"    false    "This list"
ArgParser::addArg "[q]uiet"   false    "Supress output"
ArgParser::addArg "[s]leep"   1        "Seconds to sleep"
ArgParser::addArg "v"         1        "Verbose mode"

ArgParser::parse "$@"

ArgParser::isset help && ArgParser::showArgs

ArgParser::isset "quiet" \
   && echo "Quiet!" \
   || echo "Noisy!"

local __sleep
ArgParser::tryAndGetArg sleep into __sleep \
   && echo "Sleep for $__sleep seconds" \
   || echo "No value passed for sleep"

# This way is often more convienient, but is a little slower
echo "Sleep set to: $( ArgParser::getArg sleep )"

The required BASH is a little longer than it could be, but I wanted to avoid reliance on BASH 4's associative arrays. You can also download this directly from http://nt4.com/bash/argparser.inc.sh

#!/usr/bin/env bash

# Updates to this script may be found at
# http://nt4.com/bash/argparser.inc.sh

# Example of runtime usage:
# mnc.sh --nc -q Caprica.S0*mkv *.avi *.mp3 --more-options here --host centos8.host.com

# Example of use in script (see bottom)
# Just include this file in yours, or use
# source argparser.inc.sh

unset EXPLODED
declare -a EXPLODED
function explode 
{
    local c=$# 
    (( c < 2 )) && 
    {
        echo function "$0" is missing parameters 
        return 1
    }

    local delimiter="$1"
    local string="$2"
    local limit=${3-99}

    local tmp_delim=$'\x07'
    local delin=${string//$delimiter/$tmp_delim}
    local oldifs="$IFS"

    IFS="$tmp_delim"
    EXPLODED=($delin)
    IFS="$oldifs"
}


# See: http://fvue.nl/wiki/Bash:_Passing_variables_by_reference
# Usage: local "$1" && upvar $1 "value(s)"
upvar() {
    if unset -v "$1"; then           # Unset & validate varname
        if (( $# == 2 )); then
            eval $1=\"\$2\"          # Return single value
        else
            eval $1=\(\"\${@:2}\"\)  # Return array
        fi
    fi
}

function decho
{
    :
}

function ArgParser::check
{
    __args=${#__argparser__arglist[@]}
    for (( i=0; i<__args; i++ ))
    do
        matched=0
        explode "|" "${__argparser__arglist[$i]}"
        if [ "${#1}" -eq 1 ]
        then
            if [ "${1}" == "${EXPLODED[0]}" ]
            then
                decho "Matched $1 with ${EXPLODED[0]}"
                matched=1

                break
            fi
        else
            if [ "${1}" == "${EXPLODED[1]}" ]
            then
                decho "Matched $1 with ${EXPLODED[1]}"
                matched=1

                break
            fi
        fi
    done
    (( matched == 0 )) && return 2
    # decho "Key $key has default argument of ${EXPLODED[3]}"
    if [ "${EXPLODED[3]}" == "false" ]
    then
        return 0
    else
        return 1
    fi
}

function ArgParser::set
{
    key=$3
    value="${1:-true}"
    declare -g __argpassed__$key="$value"
}

function ArgParser::parse
{

    unset __argparser__argv
    __argparser__argv=()
    # echo parsing: "$@"

    while [ -n "$1" ]
    do
        # echo "Processing $1"
        if [ "${1:0:2}" == '--' ]
        then
            key=${1:2}
            value=$2
        elif [ "${1:0:1}" == '-' ]
        then
            key=${1:1}               # Strip off leading -
            value=$2
        else
            decho "Not argument or option: '$1'" >& 2
            __argparser__argv+=( "$1" )
            shift
            continue
        fi
        # parameter=${tmp%%=*}     # Extract name.
        # value=${tmp##*=}         # Extract value.
        decho "Key: '$key', value: '$value'"
        # eval $parameter=$value
        ArgParser::check $key
        el=$?
        # echo "Check returned $el for $key"
        [ $el -eq  2 ] && decho "No match for option '$1'" >&2 # && __argparser__argv+=( "$1" )
        [ $el -eq  0 ] && decho "Matched option '${EXPLODED[2]}' with no arguments"        >&2 && ArgParser::set true "${EXPLODED[@]}"
        [ $el -eq  1 ] && decho "Matched option '${EXPLODED[2]}' with an argument of '$2'"   >&2 && ArgParser::set "$2" "${EXPLODED[@]}" && shift
        shift
    done
}

function ArgParser::isset
{
    declare -p "__argpassed__$1" > /dev/null 2>&1 && return 0
    return 1
}

function ArgParser::getArg
{
    # This one would be a bit silly, since we can only return non-integer arguments ineffeciently
    varname="__argpassed__$1"
    echo "${!varname}"
}

##
# usage: tryAndGetArg <argname> into <varname>
# returns: 0 on success, 1 on failure
function ArgParser::tryAndGetArg
{
    local __varname="__argpassed__$1"
    local __value="${!__varname}"
    test -z "$__value" && return 1
    local "$3" && upvar $3 "$__value"
    return 0
}

function ArgParser::__construct
{
    unset __argparser__arglist
    # declare -a __argparser__arglist
}

##
# @brief add command line argument
# @param 1 short and/or long, eg: [s]hort
# @param 2 default value
# @param 3 description
##
function ArgParser::addArg
{
    # check for short arg within long arg
    if [[ "$1" =~ \[(.)\] ]]
    then
        short=${BASH_REMATCH[1]}
        long=${1/\[$short\]/$short}
    else
        long=$1
    fi
    if [ "${#long}" -eq 1 ]
    then
        short=$long
        long=''
    fi
    decho short: "$short"
    decho long: "$long"
    __argparser__arglist+=("$short|$long|$1|$2|$3")
}

## 
# @brief show available command line arguments
##
function ArgParser::showArgs
{
    # declare -p | grep argparser
    printf "Usage: %s [OPTION...]\n\n" "$( basename "${BASH_SOURCE[0]}" )"
    printf "Defaults for the options are specified in brackets.\n\n";

    __args=${#__argparser__arglist[@]}
    for (( i=0; i<__args; i++ ))
    do
        local shortname=
        local fullname=
        local default=
        local description=
        local comma=

        explode "|" "${__argparser__arglist[$i]}"

        shortname="${EXPLODED[0]:+-${EXPLODED[0]}}" # String Substitution Guide: 
        fullname="${EXPLODED[1]:+--${EXPLODED[1]}}" # http://tldp.org/LDP/abs/html/parameter-substitution.html
        test -n "$shortname" \
            && test -n "$fullname" \
            && comma=","

        default="${EXPLODED[3]}"
        case $default in
            false )
                default=
                ;;
            "" )
                default=
                ;;
            * )
                default="[$default]"
        esac

        description="${EXPLODED[4]}"

        printf "  %2s%1s %-19s %s %s\n" "$shortname" "$comma" "$fullname" "$description" "$default"
    done
}

function ArgParser::test
{
    # Arguments with a default of 'false' do not take paramaters (note: default
    # values are not applied in this release)

    ArgParser::addArg "[h]elp"      false       "This list"
    ArgParser::addArg "[q]uiet" false       "Supress output"
    ArgParser::addArg "[s]leep" 1           "Seconds to sleep"
    ArgParser::addArg "v"           1           "Verbose mode"

    ArgParser::parse "$@"

    ArgParser::isset help && ArgParser::showArgs

    ArgParser::isset "quiet" \
        && echo "Quiet!" \
        || echo "Noisy!"

    local __sleep
    ArgParser::tryAndGetArg sleep into __sleep \
        && echo "Sleep for $__sleep seconds" \
        || echo "No value passed for sleep"

    # This way is often more convienient, but is a little slower
    echo "Sleep set to: $( ArgParser::getArg sleep )"

    echo "Remaining command line: ${__argparser__argv[@]}"

}

if [ "$( basename "$0" )" == "argparser.inc.sh" ]
then
    ArgParser::test "$@"
fi

---

If all your long options have unique, and matching, first characters as the short options, so for example

./slamm --chaos 23 --plenty test -quiet

Is the same as

./slamm -c 23 -p test -q

You can use this before getopts to rewrite $args:

# change long options to short options

for arg; do 
    [[ "${arg:0:1}" == "-" ]] && delim="" || delim="\""
    if [ "${arg:0:2}" == "--" ]; 
       then args="${args} -${arg:2:1}" 
       else args="${args} ${delim}${arg}${delim}"
    fi
done

# reset the incoming args
eval set -- $args

# proceed as usual
while getopts ":b:la:h" OPTION; do
    .....

Thanks for mtvee for the inspiration ;-)

---

Builtin getopts only parse short options (except in ksh93), but you can still add few lines of scripting to make getopts handles long options.

Here is a part of code found in http://www.uxora.com/unix/shell-script/22-handle-long-options-with-getopts

  #== set short options ==#
SCRIPT_OPTS=':fbF:B:-:h'
  #== set long options associated with short one ==#
typeset -A ARRAY_OPTS
ARRAY_OPTS=(
    [foo]=f
    [bar]=b
    [foobar]=F
    [barfoo]=B
    [help]=h
    [man]=h
)

  #== parse options ==#
while getopts ${SCRIPT_OPTS} OPTION ; do
    #== translate long options to short ==#
    if [[ "x$OPTION" == "x-" ]]; then
        LONG_OPTION=$OPTARG
        LONG_OPTARG=$(echo $LONG_OPTION | grep "=" | cut -d'=' -f2)
        LONG_OPTIND=-1
        [[ "x$LONG_OPTARG" = "x" ]] && LONG_OPTIND=$OPTIND || LONG_OPTION=$(echo $OPTARG | cut -d'=' -f1)
        [[ $LONG_OPTIND -ne -1 ]] && eval LONG_OPTARG="\$$LONG_OPTIND"
        OPTION=${ARRAY_OPTS[$LONG_OPTION]}
        [[ "x$OPTION" = "x" ]] &&  OPTION="?" OPTARG="-$LONG_OPTION"

        if [[ $( echo "${SCRIPT_OPTS}" | grep -c "${OPTION}:" ) -eq 1 ]]; then
            if [[ "x${LONG_OPTARG}" = "x" ]] || [[ "${LONG_OPTARG}" = -* ]]; then 
                OPTION=":" OPTARG="-$LONG_OPTION"
            else
                OPTARG="$LONG_OPTARG";
                if [[ $LONG_OPTIND -ne -1 ]]; then
                    [[ $OPTIND -le $Optnum ]] && OPTIND=$(( $OPTIND+1 ))
                    shift $OPTIND
                    OPTIND=1
                fi
            fi
        fi
    fi

    #== options follow by another option instead of argument ==#
    if [[ "x${OPTION}" != "x:" ]] && [[ "x${OPTION}" != "x?" ]] && [[ "${OPTARG}" = -* ]]; then 
        OPTARG="$OPTION" OPTION=":"
    fi

    #== manage options ==#
    case "$OPTION" in
        f  ) foo=1 bar=0                    ;;
        b  ) foo=0 bar=1                    ;;
        B  ) barfoo=${OPTARG}               ;;
        F  ) foobar=1 && foobar_name=${OPTARG} ;;
        h ) usagefull && exit 0 ;;
        : ) echo "${SCRIPT_NAME}: -$OPTARG: option requires an argument" >&2 && usage >&2 && exit 99 ;;
        ? ) echo "${SCRIPT_NAME}: -$OPTARG: unknown option" >&2 && usage >&2 && exit 99 ;;
    esac
done
shift $((${OPTIND} - 1))

Here is a test:

# Short options test
$ ./foobar_any_getopts.sh -bF "Hello world" -B 6 file1 file2
foo=0 bar=1
barfoo=6
foobar=1 foobar_name=Hello world
files=file1 file2

# Long and short options test
$ ./foobar_any_getopts.sh --bar -F Hello --barfoo 6 file1 file2
foo=0 bar=1
barfoo=6
foobar=1 foobar_name=Hello
files=file1 file2

Otherwise in recent Korn Shell ksh93, getopts can naturally parse long options and even display a man page alike. (See http://www.uxora.com/unix/shell-script/20-getopts-with-man-page-and-long-options)

---

Th built-in OS X (BSD) getopt does not support long options, but the GNU version does: brew install gnu-getopt. Then, something similar to: cp /usr/local/Cellar/gnu-getopt/1.1.6/bin/getopt /usr/local/bin/gnu-getopt.

---

A simple DIY to get only long named args:

Use:

$ ./test-args.sh --a1 a1 --a2 "a 2" --a3 --a4= --a5=a5 --a6="a 6"
a1 = "a1"
a2 = "a 2"
a3 = "TRUE"
a4 = ""
a5 = "a5"
a6 = "a 6"
a7 = ""

Script:

#!/bin/bash

function main() {
    ARGS=`getArgs "$@"`

    a1=`echo "$ARGS" | getNamedArg a1`
    a2=`echo "$ARGS" | getNamedArg a2`
    a3=`echo "$ARGS" | getNamedArg a3`
    a4=`echo "$ARGS" | getNamedArg a4`
    a5=`echo "$ARGS" | getNamedArg a5`
    a6=`echo "$ARGS" | getNamedArg a6`
    a7=`echo "$ARGS" | getNamedArg a7`

    echo "a1 = \"$a1\""
    echo "a2 = \"$a2\""
    echo "a3 = \"$a3\""
    echo "a4 = \"$a4\""
    echo "a5 = \"$a5\""
    echo "a6 = \"$a6\""
    echo "a7 = \"$a7\""

    exit 0
}


function getArgs() {
    for arg in "$@"; do
        echo "$arg"
    done
}


function getNamedArg() {
    ARG_NAME=$1

    sed --regexp-extended --quiet --expression="
        s/^--$ARG_NAME=(.*)\$/\1/p  # Get arguments in format '--arg=value': [s]ubstitute '--arg=value' by 'value', and [p]rint
        /^--$ARG_NAME\$/ {          # Get arguments in format '--arg value' ou '--arg'
            n                       # - [n]ext, because in this format, if value exists, it will be the next argument
            /^--/! p                # - If next doesn't starts with '--', it is the value of the actual argument
            /^--/ {                 # - If next do starts with '--', it is the next argument and the actual argument is a boolean one
                # Then just repla[c]ed by TRUE
                c TRUE
            }
        }
    "
}


main "$@"

---