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Default arguments handling in bash script, see blog article https://scito.ch/node/76
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#!/bin/bash | |
# Bash optional arguments demo | |
# Published in blog article https://scito.ch/node/76 or https://gist.github.com/scito/2eb40fefe672d77fee7fd41ef2456164 | |
# Three cases are supported: | |
# 1) Parameter is not present: the global default value is taken | |
# 2a) Parameter is present, but no right-hand value is given (-x or -x=): the parameter default value is taken | |
# 2b) Parameter is present, but only an equal sign is given without value (-X=): the empty string is set | |
# 3) Parameter is present with given value (-x=Y): the value is taken | |
# 4) Left over parameters are output in verbose mode (-v) | |
# ./args.sh | |
# x='X' | |
# ./args.sh -x | |
# x='Y' | |
# ./args.sh -x=Z | |
# x='Z' | |
# ./args.sh -x= | |
# x='Y' | |
# ./args.sh -X= | |
# x='X' | |
# ./args.sh --demox | |
# x='Y' | |
# ./args.sh --demox=Z | |
# x='Z' | |
# ./args.sh -x -v | |
# x='Y' | |
# Remaining arguments: '' | |
# ./args.sh -x -v -a -b c abc | |
# x='Y' | |
# Remaining arguments: '-a -b c abc' | |
x='X' | |
verbose=false | |
POSITIONAL=() | |
while test $# -gt 0; do | |
case $1 in | |
-h|--help) | |
echo "Args demo: prints value of argument x" | |
echo | |
echo "$0 [options]" | |
echo | |
echo "Options:" | |
echo "-x[=VAL], --demox[=VAL] Demo argument, default 'X' if parameter not present, default 'Y' if -x is given without right-hand value" | |
echo "-X[=VAL], --demoX[=VAL] Demo argument, default 'X' if parameter not present, default 'Y' if -X is given without right-hand value (treating -X= as empty value)" | |
echo "-v, --verbose Verbose mode: show remaining arguments" | |
echo "-h, --help Show this help" | |
echo | |
exit | |
;; | |
-x|--demox|-X|--demoX) | |
x="Y" | |
shift | |
;; | |
-x=*|--demox=*) | |
x="${1#*=}" | |
if [[ $x == "" ]]; then | |
x="Y" | |
fi | |
shift | |
;; | |
-X=*|--demoX=*) | |
x="${1#*=}" | |
shift | |
;; | |
-v|--verbose) | |
verbose=true | |
shift | |
;; | |
*) | |
POSITIONAL+=("$1") # save it in an array for later | |
shift | |
;; | |
esac | |
done | |
set -- "${POSITIONAL[@]}" # restore positional parameters | |
echo "x='$x'" | |
if $verbose; then | |
echo "Remaining arguments: '$@'" | |
fi |
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