Shell Programming and Scripting

If you have some options that take option arguments and some that don't, you'll find that getopts gives you lots of capabilities that the type of script provided in message #2 in this thread does not provide. These capabilities allow shell scripts to parse options like the standard utilities defined by the POSIX standards and the Single UNIX Specifications. (Multiple options can be grouped after a single "-", option arguments can be separate from the option flag or combined into a single operand, etc.)

For a better example of what you can do with getopts, try something like:

Code:

#!/bin/ksh
AVAR="Default avar value"
BF=
CF=
TVAR="Default tvar value"
while getopts 'a:bct:' x
do      case "$x" in
        (a)     AVAR="$OPTARG";;
        (b)     BF=1;;
        (c)     CF=1;;
        (t)     TVAR="$OPTARG";;
        (?)     echo "Usage: $0 [-bc] [-a AVAR_string] [-t TVAR_string] [file...]"
                exit 1
        esac
done
shift $((OPTIND - 1))
echo "AVAR is set to $AVAR"
if [ "$BF" == 1 ]
then    echo "Option b present"
fi
if [ "$CF" == 1 ]
then    echo "Option c present"
fi
echo "TVAR is set to $TVAR"
echo "$# file operand(s) present:"
while [ $# -gt 0 ]
do      printf "\t%s\n" $1
        shift
done
exit

Save it in a file (e.g., tester). Change the /bin/ksh in the 1st line to an absolute pathname of a standards conforming shell on your system. I use the Korn shell, but this script will work with bash and several other shells. (However, it won't work with csh or similar shells like tcsh.) Make the script executable by running the command:

Code:

chmod +x tester

and try running it with several test cases. For example:

Code:

./tester -a "a value" -c  -b
./tester -baastring -t tstring file1 file2
./tester -d file

Top class explanation Don