An example of how to use getopts in bash

Question

I want to call myscript file in this way:

$ ./myscript -s 45 -p any_string

or

$ ./myscript -h  #should display help
$ ./myscript     #should display help

My requirements are:

getopts here to get the input arguments
check that -s exists, if not return an error
check that the value after the -s is 45 or 90
check that the -p exists and there is an input string after
if the user enters ./myscript -h or just ./myscript then display help

So far, I tried this code:

#!/bin/bash
while getopts "h:s:" arg; do
  case $arg in
    h)
      echo "usage" 
      ;;
    s)
      strength=$OPTARG
      echo $strength
      ;;
  esac
done

But with that code I get errors. How to do it with Bash and getopt?

Options are supposed to be optional. If you require the value specified by -s, make it a positional argument: ./myscript 45 anystring. — chepner, Commented May 10, 2013 at 13:19
It's fine if -p is actually an option (that is, your program can proceed if it's not present). In this case, ./myscript 45 -p any_string. (I think that getopt can handle mixed options and positional arguments, whereas the bash built-in command getopts requires all positional arguments to be placed after options.) — chepner, Commented May 10, 2013 at 13:42

Adrian Frühwirth · Accepted Answer · 2013-08-14 14:58:23Z

777

#!/bin/bash

usage() { echo "Usage: $0 [-s <45|90>] [-p <string>]" 1>&2; exit 1; }

while getopts ":s:p:" o; do
    case "${o}" in
        s)
            s=${OPTARG}
            ((s == 45 || s == 90)) || usage
            ;;
        p)
            p=${OPTARG}
            ;;
        *)
            usage
            ;;
    esac
done
shift $((OPTIND-1))

if [ -z "${s}" ] || [ -z "${p}" ]; then
    usage
fi

echo "s = ${s}"
echo "p = ${p}"

Example runs:

$ ./myscript.sh
Usage: ./myscript.sh [-s <45|90>] [-p <string>]

$ ./myscript.sh -h
Usage: ./myscript.sh [-s <45|90>] [-p <string>]

$ ./myscript.sh -s "" -p ""
Usage: ./myscript.sh [-s <45|90>] [-p <string>]

$ ./myscript.sh -s 10 -p foo
Usage: ./myscript.sh [-s <45|90>] [-p <string>]

$ ./myscript.sh -s 45 -p foo
s = 45
p = foo

$ ./myscript.sh -s 90 -p bar
s = 90
p = bar

edited Aug 14, 2013 at 14:58

answered May 11, 2013 at 11:16

Adrian Frühwirth

45.8k10 gold badges63 silver badges71 bronze badges

65

In the getopts call, why is there a leading colon? When does "h" have a colon after it?
– e40
Commented Aug 14, 2013 at 14:43
16

Should usage() really return 1?
– Pithikos
Commented Sep 10, 2014 at 8:21
10

@Pithikos Good point. Common sense tells me that when invoked via -h it should return 0, upon hitting a non-existing flag it should return >0 (for the sake of simplicity I didn't differentiate between those cases and nobody forces you to print the usage text in the latter case). I have seen programs which always return != 0, though, even on -h/--help. Maybe I should update the snippet in case people use this as boilerplate (I hope not)?
– Adrian Frühwirth
Commented Sep 10, 2014 at 9:04
12

@user1011471 You are correct! Curly braces, so to speak, just aid the bash lexer in identifying variables. They are in many cases unneeded and the fact that I always use them is just a matter of personal coding style. To me, it's easier (and prettier) to just always use them instead of remembering the parsing rules with regards to ambiguity. Pretty much the same why one would write if (foo) { bar; } instead of if (foo) bar; in a C-style language (aesthetics and/or avoiding silly mistakes).
– Adrian Frühwirth
Commented Aug 12, 2015 at 9:17
14

Sadly there's no explaination at all in this answer, yet it gets upvoted. Would be nice if more information was added.
– user
Commented Apr 29, 2021 at 12:19

| Show 21 more comments

gronostaj · Accepted Answer · 2023-04-19 07:20:41Z

The problem with the original code is that:

h: expects parameter where it shouldn't, so change it into just h (without colon)
to expect -p any_string, you need to add p: to the argument list

Basically : after the option means it requires the argument.

The basic syntax of getopts is (see: man bash):

getopts OPTSTRING VARNAME [ARGS...]

where:

OPTSTRING is string with list of expected arguments,
- h - check for option -h without parameters; gives error on unsupported options;
- h: - check for option -h with parameter; gives errors on unsupported options;
- abc - check for options -a, -b, -c; gives errors on unsupported options;
- :abc - check for options -a, -b, -c; silences errors on unsupported options;
  
  ^{Notes: In other words, colon in front of options allows you handle the errors in your code. Variable will contain ? in the case of unsupported option, : in the case of missing value.}
OPTARG - is set to current argument value,
OPTERR - indicates if Bash should display error messages.

So the code can be:

#!/usr/bin/env bash
usage() { echo "$0 usage:" && grep " .)\ #" $0; exit 0; }
[ $# -eq 0 ] && usage
while getopts ":hs:p:" arg; do
  case $arg in
    p) # Specify p value.
      echo "p is ${OPTARG}"
      ;;
    s) # Specify strength, either 45 or 90.
      strength=${OPTARG}
      [ $strength -eq 45 -o $strength -eq 90 ] \
        && echo "Strength is $strength." \
        || echo "Strength needs to be either 45 or 90, $strength found instead."
      ;;
    h | *) # Display help.
      usage
      exit 0
      ;;
  esac
done

Example usage:

$ ./foo.sh 
./foo.sh usage:
    p) # Specify p value.
    s) # Specify strength, either 45 or 90.
    h | *) # Display help.
$ ./foo.sh -s 123 -p any_string
Strength needs to be either 45 or 90, 123 found instead.
p is any_string
$ ./foo.sh -s 90 -p any_string
Strength is 90.
p is any_string

See: Small getopts tutorial at Bash Hackers Wiki

Change the usage function to this: usage() { echo "$0 usage:" && grep "[[:space:]].)\ #" $0 | sed 's/#//' | sed -r 's/([a-z])\)/-\1/'; exit 0; }. It only accounts for a single whitespace character before the letter option, removes the # from the comment and prepends a '-' before the letter option making it clearer for the command. — poagester, Commented Oct 5, 2016 at 19:55
@kenorb: Colon in front of options doesn't ignore unsupported options but silences errors from bash and allows you handle it in your code. Variable will contain '?' in the case of unsupported option and ':' in the case of missing value. — Hynek -Pichi- Vychodil, Commented Feb 6, 2017 at 7:42
Thanks for the detailed docs, wasn't able to get the : right until I saw these notes. We need to add a : to the options where we are expecting an argument. — Aukhan, Commented Feb 25, 2019 at 7:22
This is a great example, and I've used it in my scripts. However, under the case for option "h", the exit 0 isn't needed (nor is it ever reached) as usage calls exit 0 instead. — Greenonline, Commented Oct 23, 2022 at 10:03

5 revs, 4 users 96% · Accepted Answer · 2022-12-11 08:39:22Z

Use getopt

Why getopt?

To parse elaborated command-line arguments to avoid confusion and clarify the options we are parsing so that reader of the commands can understand what's happening.

What is getopt?

getopt is used to break up (parse) options in command lines for easy parsing by shell procedures, and to check for legal options. It uses the GNU getopt(3) routines to do this.

getopt can have following types of options.

No-value options
key-value pair options

Note: In this document, during explaining syntax:

Anything inside [ ] is optional parameter in the syntax/examples.
<value> is a place holder, which mean it should be substituted with an actual value.

HOW TO USE getopt?

Syntax: First Form

getopt optstring parameters

Examples:

# This is correct
getopt "hv:t::" -v 123 -t123  
getopt "hv:t::" -v123 -t123  # -v and 123 doesn't have whitespace

# -h takes no value.
getopt "hv:t::" -h -v123


# This is wrong. after -t can't have whitespace.
# Only optional params cannot have whitespace between key and value
getopt "hv:t::" -v 123 -t 123

# Multiple arguments that takes value.
getopt "h:v:t::g::" -h abc -v 123 -t21

# Multiple arguments without value
# All of these are correct
getopt "hvt" -htv
getopt "hvt" -h -t -v
getopt "hvt" -tv -h

Here h,v,t are the options and -h -v -t is how options should be given in command-line.

'h' is a no-value option.
'v:' implies that option -v has value and is a mandatory option. ':' means has a value.
't::' implies that option -t has value but is optional. '::' means optional.

In optional param, value cannot have whitespace separation with the option. So, in "-t123" example, -t is option 123 is value.

Syntax: Second Form

getopt [getopt_options] [--] optstring parameters

Here after getopt is split into five parts

The command itself i.e. getopt
The getopt_options, it describes how to parse the arguments. single dash long options, double dash options.
--, separates out the getopt_options from the options you want to parse and the allowed short options
The short options, is taken immediately after -- is found. Just like the Form first syntax.
The parameters, these are the options that you have passed into the program. The options you want to parse and get the actual values set on them.

Examples

getopt -l "name:,version::,verbose" -- "n:v::V" --name=Karthik -version=5.2 -verbose

Syntax: Third Form

getopt [getopt_options] -o|--options optstring [getopt_options] [--] [parameters]

Here after getopt is split into five parts

The command itself i.e. getopt
The getopt_options, it describes how to parse the arguments. single dash long options, double dash options.
The short options i.e. -o or --options. Just like the Form first syntax but with option "-o" and before the "--" (double dash).
--, separates out the getopt_options from the options you want to parse and the allowed short options
The parameters, these are the options that you have passed into the program. The options you want to parse and get the actual values set on them.

Examples

getopt -l "name:,version::,verbose" -a -o "n:v::V" -- -name=Karthik -version=5.2 -verbose

GETOPT_OPTIONS

getopt_options changes the way command-line params are parsed.

Below are some of the getopt_options

Option: -l or --longoptions

Means getopt command should allow multi-character options to be recognised. Multiple options are separated by comma.

For example, --name=Karthik is a long option sent in command line. In getopt, usage of long options are like

getopt -l "name:,version" -- "" --name=Karthik

Since name: is specified, the option should contain a value

Option: -a or --alternative

Means getopt command should allow long option to have a single dash '-' rather than double dash '--'.

Example, instead of --name=Karthik you could use just -name=Karthik

getopt -a -l "name:,version" -- "" -name=Karthik

A complete script example with the code:

#!/bin/bash

# filename: commandLine.sh
# author: @theBuzzyCoder

showHelp() {
# `cat << EOF` This means that cat should stop reading when EOF is detected
cat << EOF  
Usage: ./installer -v <espo-version> [-hrV]
Install Pre-requisites for EspoCRM with docker in Development mode

-h, -help,          --help                  Display help

-v, -espo-version,  --espo-version          Set and Download specific version of EspoCRM

-r, -rebuild,       --rebuild               Rebuild php vendor directory using composer and compiled css using grunt

-V, -verbose,       --verbose               Run script in verbose mode. Will print out each step of execution.

EOF
# EOF is found above and hence cat command stops reading. This is equivalent to echo but much neater when printing out.
}


export version=0
export verbose=0
export rebuilt=0

# $@ is all command line parameters passed to the script.
# -o is for short options like -v
# -l is for long options with double dash like --version
# the comma separates different long options
# -a is for long options with single dash like -version
options=$(getopt -l "help,version:,verbose,rebuild,dryrun" -o "hv:Vrd" -a -- "$@")

# set --:
# If no arguments follow this option, then the positional parameters are unset. Otherwise, the positional parameters 
# are set to the arguments, even if some of them begin with a ‘-’.
eval set -- "$options"

while true
do
case "$1" in
-h|--help) 
    showHelp
    exit 0
    ;;
-v|--version) 
    shift
    export version="$1"
    ;;
-V|--verbose)
    export verbose=1
    set -xv  # Set xtrace and verbose mode.
    ;;
-r|--rebuild)
    export rebuild=1
    ;;
--)
    shift
    break;;
esac
shift
done

Running this script file:

# With short options grouped together and long option
# With double dash '--version'

bash commandLine.sh --version=1.0 -rV
# With short options grouped together and long option
# With single dash '-version'

bash commandLine.sh -version=1.0 -rV

# OR with short option that takes value, value separated by whitespace
# by key

bash commandLine.sh -v 1.0 -rV

# OR with short option that takes value, value without whitespace
# separation from key.

bash commandLine.sh -v1.0 -rV

# OR Separating individual short options

bash commandLine.sh -v1.0 -r -V

getopt vs getopts .. very different cross platform compliance — shadowbq, Commented Jan 29, 2020 at 14:29
While I too find GNU getopt superior, it's not built in on BSD systems (like macOS) so if your goal is cross platform compatibility, go with getopts — Győri Sándor, Commented Jun 16, 2021 at 10:17
getopt from macOS Monterey is very old (1999) and simple. A better one is brew install getopt. So I don't suggest getopt any more. — DawnSong, Commented May 26, 2022 at 2:57
You should consider writing a book on getopt for O'Reilly. More seriously, the shortest answer are the best. People who get here already know what is getopt, and if they don't it's not your role to explain them in lengthy details every aspect of the command. — Eric, Commented Apr 18, 2023 at 9:22

vaeVictis · Accepted Answer · 2021-11-21 02:29:29Z

49

The example packaged with getopt (my distro put it in /usr/share/getopt/getopt-parse.bash) looks like it covers all of your cases:

#!/bin/bash

# A small example program for using the new getopt(1) program.
# This program will only work with bash(1)
# An similar program using the tcsh(1) script language can be found
# as parse.tcsh

# Example input and output (from the bash prompt):
# ./parse.bash -a par1 'another arg' --c-long 'wow!*\?' -cmore -b " very long "
# Option a
# Option c, no argument
# Option c, argument 'more'
# Option b, argument ' very long '
# Remaining arguments:
# --> 'par1'
# --> 'another arg'
# --> 'wow!*\?'

# Note that we use `"$@"' to let each command-line parameter expand to a 
# separate word. The quotes around '$@' are essential!
# We need TEMP as the `eval set --' would nuke the return value of getopt.
TEMP=$(getopt -o ab:c:: --long a-long,b-long:,c-long:: \
              -n 'example.bash' -- "$@")

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

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

while true ; do
    case "$1" in
        -a|--a-long) echo "Option a" ; shift ;;
        -b|--b-long) echo "Option b, argument '$2'" ; shift 2 ;;
        -c|--c-long) 
            # c has an optional argument. As we are in quoted mode,
            # an empty parameter will be generated if its optional
            # argument is not found.
            case "$2" in
                "") echo "Option c, no argument"; shift 2 ;;
                *)  echo "Option c, argument '$2'" ; shift 2 ;;
            esac ;;
        --) shift ; break ;;
        *) echo "Internal error!" ; exit 1 ;;
    esac
done
echo "Remaining arguments:"
for arg do echo '--> '"'$arg'" ; done

edited Nov 21, 2021 at 2:29

vaeVictis

5021 gold badge3 silver badges15 bronze badges

answered May 10, 2013 at 13:21

Brian Cain

14.6k3 gold badges52 silver badges89 bronze badges

12

The external command getopt(1) is never safe to use, unless you know it is GNU getopt, you call it in a GNU-specific way, and you ensure that GETOPT_COMPATIBLE is not in the environment. Use getopts (shell builtin) instead, or simply loop over the positional parameters.
– Gilles Quénot
Commented Aug 14, 2013 at 16:52
18

Eh, no external command is safe to use by that standard. Built in getopts is missing crucial features and if you want to check for GETOPT_COMPATIBLE that's easier than porting getopt's features.
– Michael Terry
Commented Sep 12, 2014 at 18:26
getopt is in the util-linux package, so unless you're trying to support many different *nix'es at once, you'll probably be fine, but it's of course a good thing to keep in mind.
– Steen Schütt
Commented Jun 4, 2021 at 8:16
1

why eval set -- "$TEMP" and not just set -- "$TEMP" ?
– onlycparra
Commented Dec 11, 2022 at 9:19
Here's up to date source code for the example which is mentioned above: github.com/util-linux/util-linux/blob/master/misc-utils/…
– GrabbenD
Commented Nov 3, 2023 at 20:58

Add a comment |

Ciro Santilli OurBigBook.com · Accepted Answer · 2018-03-30 11:19:35Z

POSIX 7 example

It is also worth checking the example from the standard: http://pubs.opengroup.org/onlinepubs/9699919799/utilities/getopts.html

aflag=
bflag=
while getopts ab: name
do
    case $name in
    a)    aflag=1;;
    b)    bflag=1
          bval="$OPTARG";;
    ?)   printf "Usage: %s: [-a] [-b value] args\n" $0
          exit 2;;
    esac
done
if [ ! -z "$aflag" ]; then
    printf "Option -a specified\n"
fi
if [ ! -z "$bflag" ]; then
    printf 'Option -b "%s" specified\n' "$bval"
fi
shift $(($OPTIND - 1))
printf "Remaining arguments are: %s\n" "$*"

And then we can try it out:

$ sh a.sh
Remaining arguments are: 
$ sh a.sh -a
Option -a specified
Remaining arguments are: 
$ sh a.sh -b
No arg for -b option
Usage: a.sh: [-a] [-b value] args
$ sh a.sh -b myval
Option -b "myval" specified
Remaining arguments are: 
$ sh a.sh -a -b myval
Option -a specified
Option -b "myval" specified
Remaining arguments are: 
$ sh a.sh remain
Remaining arguments are: remain
$ sh a.sh -- -a remain
Remaining arguments are: -a remain

Tested in Ubuntu 17.10, sh is dash 0.5.8.

Sebastian · Accepted Answer · 2017-04-21 00:45:33Z

I know that this is already answered, but for the record and for anyone with the same requeriments as me I decided to post this related answer. The code is flooded with comments to explain the code.

Updated answer:

Save the file as getopt.sh:

#!/bin/bash

function get_variable_name_for_option {
    local OPT_DESC=${1}
    local OPTION=${2}
    local VAR=$(echo ${OPT_DESC} | sed -e "s/.*\[\?-${OPTION} \([A-Z_]\+\).*/\1/g" -e "s/.*\[\?-\(${OPTION}\).*/\1FLAG/g")

    if [[ "${VAR}" == "${1}" ]]; then
        echo ""
    else
        echo ${VAR}
    fi
}

function parse_options {
    local OPT_DESC=${1}
    local INPUT=$(get_input_for_getopts "${OPT_DESC}")

    shift
    while getopts ${INPUT} OPTION ${@};
    do
        [ ${OPTION} == "?" ] && usage
        VARNAME=$(get_variable_name_for_option "${OPT_DESC}" "${OPTION}")
            [ "${VARNAME}" != "" ] && eval "${VARNAME}=${OPTARG:-true}" # && printf "\t%s\n" "* Declaring ${VARNAME}=${!VARNAME} -- OPTIONS='$OPTION'"
    done

    check_for_required "${OPT_DESC}"

}

function check_for_required {
    local OPT_DESC=${1}
    local REQUIRED=$(get_required "${OPT_DESC}" | sed -e "s/\://g")
    while test -n "${REQUIRED}"; do
        OPTION=${REQUIRED:0:1}
        VARNAME=$(get_variable_name_for_option "${OPT_DESC}" "${OPTION}")
                [ -z "${!VARNAME}" ] && printf "ERROR: %s\n" "Option -${OPTION} must been set." && usage
        REQUIRED=${REQUIRED:1}
    done
}

function get_input_for_getopts {
    local OPT_DESC=${1}
    echo ${OPT_DESC} | sed -e "s/\([a-zA-Z]\) [A-Z_]\+/\1:/g" -e "s/[][ -]//g"
}

function get_optional {
    local OPT_DESC=${1}
    echo ${OPT_DESC} | sed -e "s/[^[]*\(\[[^]]*\]\)[^[]*/\1/g" -e "s/\([a-zA-Z]\) [A-Z_]\+/\1:/g" -e "s/[][ -]//g"
}

function get_required {
    local OPT_DESC=${1}
    echo ${OPT_DESC} | sed -e "s/\([a-zA-Z]\) [A-Z_]\+/\1:/g" -e "s/\[[^[]*\]//g" -e "s/[][ -]//g"
}

function usage {
    printf "Usage:\n\t%s\n" "${0} ${OPT_DESC}"
    exit 10
}

Then you can use it like this:

#!/bin/bash
#
# [ and ] defines optional arguments
#

# location to getopts.sh file
source ./getopt.sh
USAGE="-u USER -d DATABASE -p PASS -s SID [ -a START_DATE_TIME ]"
parse_options "${USAGE}" ${@}

echo ${USER}
echo ${START_DATE_TIME}

Old answer:

I recently needed to use a generic approach. I came across with this solution:

#!/bin/bash
# Option Description:
# -------------------
#
# Option description is based on getopts bash builtin. The description adds a variable name feature to be used
# on future checks for required or optional values.
# The option description adds "=>VARIABLE_NAME" string. Variable name should be UPPERCASE. Valid characters
# are [A-Z_]*.
#
# A option description example:
#   OPT_DESC="a:=>A_VARIABLE|b:=>B_VARIABLE|c=>C_VARIABLE"
#
# -a option will require a value (the colon means that) and should be saved in variable A_VARIABLE.
# "|" is used to separate options description.
# -b option rule applies the same as -a.
# -c option doesn't require a value (the colon absense means that) and its existence should be set in C_VARIABLE
#
#   ~$ echo get_options ${OPT_DESC}
#   a:b:c
#   ~$
#


# Required options 
REQUIRED_DESC="a:=>REQ_A_VAR_VALUE|B:=>REQ_B_VAR_VALUE|c=>REQ_C_VAR_FLAG"

# Optional options (duh)
OPTIONAL_DESC="P:=>OPT_P_VAR_VALUE|r=>OPT_R_VAR_FLAG"

function usage {
    IFS="|"
    printf "%s" ${0}
    for i in ${REQUIRED_DESC};
    do
        VARNAME=$(echo $i | sed -e "s/.*=>//g")
    printf " %s" "-${i:0:1} $VARNAME"
    done

    for i in ${OPTIONAL_DESC};
    do
        VARNAME=$(echo $i | sed -e "s/.*=>//g")
        printf " %s" "[-${i:0:1} $VARNAME]"
    done
    printf "\n"
    unset IFS
    exit
}

# Auxiliary function that returns options characters to be passed
# into 'getopts' from a option description.
# Arguments:
#   $1: The options description (SEE TOP)
#
# Example:
#   OPT_DESC="h:=>H_VAR|f:=>F_VAR|P=>P_VAR|W=>W_VAR"
#   OPTIONS=$(get_options ${OPT_DESC})
#   echo "${OPTIONS}"
#
# Output:
#   "h:f:PW"
function get_options {
    echo ${1} | sed -e "s/\([a-zA-Z]\:\?\)=>[A-Z_]*|\?/\1/g"
}

# Auxiliary function that returns all variable names separated by '|'
# Arguments:
#       $1: The options description (SEE TOP)
#
# Example:
#       OPT_DESC="h:=>H_VAR|f:=>F_VAR|P=>P_VAR|W=>W_VAR"
#       VARNAMES=$(get_values ${OPT_DESC})
#       echo "${VARNAMES}"
#
# Output:
#       "H_VAR|F_VAR|P_VAR|W_VAR"
function get_variables {
    echo ${1} | sed -e "s/[a-zA-Z]\:\?=>\([^|]*\)/\1/g"
}

# Auxiliary function that returns the variable name based on the
# option passed by.
# Arguments:
#   $1: The options description (SEE TOP)
#   $2: The option which the variable name wants to be retrieved
#
# Example:
#   OPT_DESC="h:=>H_VAR|f:=>F_VAR|P=>P_VAR|W=>W_VAR"
#   H_VAR=$(get_variable_name ${OPT_DESC} "h")
#   echo "${H_VAR}"
#
# Output:
#   "H_VAR"
function get_variable_name {
    VAR=$(echo ${1} | sed -e "s/.*${2}\:\?=>\([^|]*\).*/\1/g")
    if [[ ${VAR} == ${1} ]]; then
        echo ""
    else
        echo ${VAR}
    fi
}

# Gets the required options from the required description
REQUIRED=$(get_options ${REQUIRED_DESC})

# Gets the optional options (duh) from the optional description
OPTIONAL=$(get_options ${OPTIONAL_DESC})

# or... $(get_options "${OPTIONAL_DESC}|${REQUIRED_DESC}")

# The colon at starts instructs getopts to remain silent
while getopts ":${REQUIRED}${OPTIONAL}" OPTION
do
    [[ ${OPTION} == ":" ]] && usage
    VAR=$(get_variable_name "${REQUIRED_DESC}|${OPTIONAL_DESC}" ${OPTION})
    [[ -n ${VAR} ]] && eval "$VAR=${OPTARG}"
done

shift $(($OPTIND - 1))

# Checks for required options. Report an error and exits if
# required options are missing.

# Using function version ...
VARS=$(get_variables ${REQUIRED_DESC})
IFS="|"
for VARNAME in $VARS;
do
    [[ -v ${VARNAME} ]] || usage
done
unset IFS

# ... or using IFS Version (no function)
OLDIFS=${IFS}
IFS="|"
for i in ${REQUIRED_DESC};
do
    VARNAME=$(echo $i | sed -e "s/.*=>//g")
    [[ -v ${VARNAME} ]] || usage
    printf "%s %s %s\n" "-${i:0:1}" "${!VARNAME:=present}" "${VARNAME}"
done
IFS=${OLDIFS}

I didn't test this roughly, so I could have some bugs in there.

If you're using getopts in a function, add local OPTIND OPTARG to the function — glenn jackman, Commented Mar 9, 2020 at 17:30
@glennjackman actually it's more like a sed approach rather than using getopts — Sebastian, Commented Mar 10, 2020 at 20:47
I get ./getopt.sh: line 38: : invalid variable name which points to the second last line in the while loop of check_for_required() when running the example. — pat-s, Commented Nov 22, 2021 at 8:30
@pat-s can you post a gist to your example so maybe I can help you? — Sebastian, Commented Nov 23, 2021 at 10:19
@Sebastian Appreciated. I went with the approach of stackoverflow.com/a/61055114/4185785 for now, which seems to work. I assume the mistake must be on my side. Thanks for sharing your solution! — pat-s, Commented Dec 1, 2021 at 7:59

Greenonline · Accepted Answer · 2022-12-07 04:20:47Z

getopts and getopt are very limited. While getopt is suggested not to be used at all, it does offer long options. Whereas getopts does only allow single character options such as -a -b. There are a few more disadvantages when using either one.

So I've written a small script that replaces getopts and getopt. It's a start, it could probably be improved a lot.

Update 08-04-2020: I've added support for hyphens e.g. --package-name.

Usage: "./script.sh package install --package "name with space" --build --archive"

# Example:
# parseArguments "${@}"
# echo "${ARG_0}" -> package
# echo "${ARG_1}" -> install
# echo "${ARG_PACKAGE}" -> "name with space"
# echo "${ARG_BUILD}" -> 1 (true)
# echo "${ARG_ARCHIVE}" -> 1 (true)
function parseArguments() {
  PREVIOUS_ITEM=''
  COUNT=0
  for CURRENT_ITEM in "${@}"
  do
    if [[ ${CURRENT_ITEM} == "--"* ]]; then
      printf -v "ARG_$(formatArgument "${CURRENT_ITEM}")" "%s" "1" # could set this to empty string and check with [ -z "${ARG_ITEM-x}" ] if it's set, but empty.
    else
      if [[ $PREVIOUS_ITEM == "--"* ]]; then
        printf -v "ARG_$(formatArgument "${PREVIOUS_ITEM}")" "%s" "${CURRENT_ITEM}"
      else
        printf -v "ARG_${COUNT}" "%s" "${CURRENT_ITEM}"
      fi
    fi

    PREVIOUS_ITEM="${CURRENT_ITEM}"
    (( COUNT++ ))
  done
}

# Format argument.
function formatArgument() {
  ARGUMENT="${1^^}" # Capitalize.
  ARGUMENT="${ARGUMENT/--/}" # Remove "--".
  ARGUMENT="${ARGUMENT//-/_}" # Replace "-" with "_".
  echo "${ARGUMENT}"
}

This doesn't answer the question but this is some very interesting code that provides an alternative approach to the problem. Thanks for sharing. — TonyG, Commented Sep 22, 2020 at 22:26
+1 - You should probably put this on github/gitlab, to allow for a collaborative effort (people raising issues for bugs/improvements, etc.). Then add the link to this answer. — Greenonline, Commented Dec 6, 2022 at 22:38

Greenonline · Accepted Answer · 2022-12-06 20:39:15Z

Turning the huge one-liner in Mark G.'s comment (under Adrian Frühwirth's answer) into a more readable answer - this shows how to avoid using getopts in order to get optional arguments:

usage() { 
    printf "Usage: %s <req> [<-s|--sopt> <45|90>] [<-p|--popt> <string>]\n" "$0"; 
    return 1; 
}; 

main() { 
    req="${1:?$(usage)}";
    shift; 
    s="";
    p="";
    while [ "$#" -ge 1 ]; do
        case "$1" in 
            -s|--sopt) 
                shift;
                s="${1:?$(usage)}";
                [ "$s" -eq 45 ] || [ "$s" -eq 90 ] || { 
                    usage; 
                    return 1; 
                } 
                ;; 
            -p|--popt) 
                shift; 
                p="${1:?$(usage)}" 
                ;; 
            *) 
                usage;
                return 1 
                ;; 
        esac; 
        shift;
    done; 
    printf "req = %s\ns = %s\np = %s\n" "$req" "$s" "$p"; 
};

main "$@"

As noted in n.caillou's comment:

it will fail if there's no space between the options and their argument.

However, to make it more POSIX compliant (from Mark G.'s other comment):

        case "$1" in 
            -s*)
                s=${1#-s}; 
                if [ -z "$s" ]; 
                    shift; 
                    s=$1; 
                fi

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