| created on | January 18, 2022 |
There are several methods for the parsing options / parameters supplied to the shell script .
space-separated
while [[ $# -gt 0 ]]; do
key="$1"
shift
case $key in
-w|--what)
what="$1"
shift
;;
-e|--ever)
ever="$1"
shift # past value
;;
-s|--simplified)
simplified=true # note we don't shift here
;;
*) # everything else
printf "munching $1, doesn't apply here" # same as above, no shift here
;;
esac
done
equals-separated
while [[ $# -gt 0 ]]; do
key="$1"
shift
case $key in
-w=*|--what=*)
what="${i#*=}"
shift
;;
-e=*|--ever=*)
ever="${i#*=}"
shift # past value
;;
-s|--simplified)
simplified=true # note we don't shift here
;;
*) # everything else
printf "munching $1, doesn't apply here" # same as above, no shift here
;;
esac
done
getopts
# POSIX variable
OPTIND=1 # reset getopts (might have used before in the shell)
while getopts "wes:" key; do
case "$key" in
w)
what=$OPTARG
;;
e)
ever=$OPTARG
;;
f)
simplified="true"
;;
esac
done
shift $((OPTIND-1))
getopt
- you need to call getopts several times. each time it will use the next positional parameter and a possible argument, if parsable, and provide it.
- getopts sets an exit status of FALSE when there’s nothing left to parse
- getopts will parse options and their possible arguments. will stop parsing on the first
non-option argument (a string that doesn’t begin with a hyphen (-) that isn’t an argument
for any option in front of it). also stops parsing when encountering – (double-hyphen,
which means end of options).
- more portable, works in other shells like dash.
- can handle multiple single options like -we whatever in the typical Unix way.
- can only handle short options
getopt manual: https://wiki.bash-hackers.org/howto/getopts_tutorial
getopt vs getopts
|
getopt |
getopts |
| standards |
none |
POSIX, Unix, Linux LSB |
| long options |
yes |
no |
| optional args |
? |
no |