I wish to have long and short forms of command line options invoked using my shell script.
I know that getopts
can be used, but like in Perl, I have not
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:
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 $*
The accepted answer does a very nice job of pointing out all the shortcomings of bash built-in getopts
. The answer ends with:
So while it is possible to write more code to work around the lack of support for long options, this is a lot more work and partially defeats the purpose of using a getopt parser to simplify your code.
And even though I agree in principle with that statement, I feel that the number of times we all implemented this feature in various scripts justifies putting a bit of effort into creating a "standardised", well tested solution.
As such, I've "upgraded" bash built in getopts
by implementing getopts_long in pure bash, with no external dependencies. The usage of the function is 100% compatible with the built-in getopts
.
By including getopts_long
(which is hosted on GitHub) in a script, the answer to the original question can be implemented as simply as:
source "${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 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 ${arguments[index]}" ;;
esac
done
exit;
Am I being dumb or something? getopt
and getopts
are so confusing.
In order to stay cross-platform compatible, and avoid the reliance on external executables, I ported some code from another language.
I find it very easy to use, here is an example:
ArgParser::addArg "[h]elp" false "This list"
ArgParser::addArg "[q]uiet" false "Supress output"
ArgParser::addArg "[s]leep" 1 "Seconds to sleep"
ArgParser::addArg "v" 1 "Verbose mode"
ArgParser::parse "$@"
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
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
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 can be harvested with a simple replacement: ${OPTARG#*=}
.
In this example, -b
and -c
(and their long forms, --bravo
and --charlie
) have mandatory arguments. Arguments to long options come after equals signs, e.g. --bravo=foo
(space delimiters for long options would be hard to implement, see below).
Because this uses the getopts builtin, this solution supports usage like cmd --bravo=foo -ac FILE
(which has combined options -a
and -c
and interleaves long options with standard options) while most other answers here either struggle or fail to do that.
die() { echo "$*" >&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 is because this implementation assumes it was a short option. You could track that with an extra variable in the long option stanza 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.
(A note about all-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 $OPTARG
, but this does break that convention. I think it fits because this is something the system should have done, and it should be safe because there are no standards (afaik) that use such a variable.)
To complain about unexpected arguments to long options, mimic what we did for mandatory arguments: use a helper function. Just flip the test around to complain about an argument when one isn't expected:
no_arg() { if [ -n "$OPTARG" ]; then die "No arg allowed for --$OPT option"; fi; }
An older version of this answer had an attempt at accepting long options with space-delimited arguments, but it was not reliable; getopts
could prematurely terminate on the assumption that the argument was beyond its scope and manually incrementing $OPTIND
doesn't work in all shells.
This would be accomplished using one of these techniques depending on your shell:
eval "bravo=\"\$$OPTIND\""
bravo="${!OPTIND}"
bravo="${(P)OPTIND}"
and then concluded with something like [ $# -gt $OPTIND ] && OPTIND=$((OPTIND+1))