I have a shell script which takes 1 mandatory argument and upto 3 optional arguments and I want to enhance the script by able to pass one more additional argument without breaking the current design . That is if my argument is n and existing arguments are a and b c and d the following should work
./script.sh a b c d n
./script.sh a n
./script.sh a b n
./script.sh a b c n
You could check if the last argument is n. If so, remove it from the argument list and add the rest to an array, else add all the arguments to an array.
if [[ "${@: -1}" = n ]]; then
for j in "${@:1:$(($#-1))}"; do
var+=($j)
done
else
for j; do
var+=($j)
done
fi
echo "${var[@]}"
This would produce:
a b c
when the arguments to the script are a b c and a b c n.
Not elegant, but straightforward:
case $# in
0|1) printf >&2 "Too few arguments\n"; exit 1
;;
2) first=$1
second=$2
;;
3) first=$1
optional_a=$2
second=$3
;;
4) first=$1
optional_a=$2
optional_b=$3
second=$4
;;
5) first=$1
optional_a=$2
optional_b=$3
optional_c=$4
second=$5
;;
*) printf >&2 "Too many optional arguments\n"; exit 1
;;
esac
The two required arguments are in first and second; the three optional arguments are in optional_a, optional_b, and optional_c, respectively.
"${var[@]}"for iterating over arrays --${var[*]}concatenates into a scalar, then string-splits and glob-expands it."two words".var=( "$@" )-- then you can have however many arguments you need.