This post covers a relatively straightforward method of parsing commandline arguments. All commandline arguments take the form of -p=value or –parameter=value. A safe delimeter is used internally so the value can contain an equals sign.

Software Versions

$ date -u "+%Y-%m-%d %H:%M:%S +0000"
2017-01-25 14:27:00 +0000
$ uname -vm
FreeBSD 12.0-CURRENT #18 4f888bf(drm-next): Wed Jan 18 14:31:26 UTC 2017 root@gauntlet:/usr/obj/usr/src/sys/GENERIC amd64

Instructions

The basic strategy looks like this, with a safe delimiter.

parse_args() {
SAFE_DELIMITER="$(printf "\a")"
while [ "$1" != "" ]
do
PARAM=$(echo $1 | cut -f1 -d=)
VALUE=$(echo $1 | sed "s/=/${SAFE_DELIMITER}/" | cut -f2 "-d${SAFE_DELIMITER}")

case $PARAM in
-h | --help)
usage
exit
;;
-v | --variable)
G_VARIABLE="${VALUE}"
;;
*)
echo "ERROR: Unknown parameter ${PARAM}"
usage
exit 1
;;
esac
shift
done
}

A complete template example looks something like this.

#!/bin/sh

set_defaults() {
G_URL="https://www.google.com"
G_CREDENTIALS="username:password"
}

usage() {
set_defaults
cat <<-EOF
./param.sh
Parameters:
-h | --help:
Show this help.
-u | --url)
URL
Default:
${G_URL}
-l=username:password | --login=username:password)
Username and password login credentials.
Default:
${G_CREDENTIALS}
EOF
}

parse_args() {
set_defaults
SAFE_DELIMITER="$(printf "\a")"
while [ "$1" != "" ]
do
PARAM=$(echo $1 | cut -f1 -d=)
VALUE=$(echo $1 | sed "s/=/${SAFE_DELIMITER}/" | cut -f2 "-d${SAFE_DELIMITER}")

case $PARAM in
-h | --help)
usage
exit
;;
-u | --url)
G_URL="${VALUE}"
;;
-l | --login)
G_CREDENTIALS="${VALUE}"
;;
*)
echo "ERROR: Unknown parameter ${PARAM}"
usage
exit 1
;;
esac
shift
done
}

main() {
parse_args $@
echo "URL=${G_URL}"
echo "CREDENTIALS=$(echo "${G_CREDENTIALS}" | sed 's/:.*/:********/')"
}

main $@