Problem with getopts

Shell Programming and Scripting
1

I need to parse parameters but the arguments could be NULL,example:

> cat getopts.sh  
while getopts "a:b:" opt 2>/dev/null
do
    case "${opt}" in
      a)   echo "A:${OPTARG}" ;;
      b)   echo "B:${OPTARG}" ;;
      *)   exit 1 ;;
    esac
done

> getopts.sh -a TEST1 -b TEST2
A:TEST1
B:TEST2

> getopts.sh -a -b TEST2      
A:-b

The first posted execution of the script works fine , but i have a problem with the second one, getopts uses the -b parameter as the argument of the -a one :frowning:

How can i avoid this??

Thank u all in advance.

2

Try a quick fix!
if you MUST have "-a xx AND -b zz" on the command line then add this to your code.....

if [ $# != 4 ]
then
echo "Usage; `basename $0` -a value -b value'
exit 9
fi

while getopts "a:b:" opt 2>/dev/null
do
case "${opt}" in
a) echo "A:${OPTARG}" ;;
b) echo "B:${OPTARG}" ;;
*) exit 1 ;;
esac
done

> getopts.sh -a TEST1 -b TEST2
A:TEST1
B:TEST2

> getopts.sh -a -b TEST2
Usage; getopts.sh -a value -b value

3

Thank�s for the reply ,however that doesn't solve my issue.

The key point here is that i need a way to handle with NULL/NOT NULL arguments.
So, in the example previously posted , the result of:

getopts.sh -a -b TEST2

Must be:

A:
B:TEST2

I know i can use other scripting tools , but i would like to do it with getopts.

Thank you all.

Cheers

4

Hi,
You can achieve the same without using getopts :

#!/usr/bin/bash

ARGUMENTS="a:b"
check_in_args()
{
	PAT=`echo ${ARGUMENTS} | awk -F: -v arg=$1 '{
			for(i=1;i<=NF;i++)
			{
				if("-" $i == arg)
				{
					printf("FOUND");
					break;
				}
			}
		}'`
	if [ "${PAT}" = "FOUND" ]
	then
		return 1
	else
		return 0
	fi
}

while [ $# -ne 0 ]
do
	case $1 in
	-a)
		check_in_args $2 RET
		if [ $? -eq 1 ]
		then
			A_VAL=""
		else
			A_VAL="$2"
			shift
		fi
	;;
	-b)
		check_in_args $2 RET
		if [ "${RET}" = "1" ]
		then
			B_VAL=""
		else
			B_VAL="$2"
			shift
		fi
	;;
	*)
	;;
	esac
	shift
done
echo "A:${A_VAL}"
echo "B:${B_VAL}"

Thanks
Raghu

5

NULL arguments are not a problem. This is how to do a NULL argument:

getopts.sh -a "" -b TEST2

What you want is for a missing argument to be treated as NULL. Suppose that I want to run the script only using the -a option and I want the argument to the -a option to be "-b". This why "getopts.sh -a -b" must be treated the way it is. What I have sometimes done in cases like this is to use -a and -b which expect no arguments and -A and -B that demand an argument. The only other solution is to give up on getopts as Raghu suggested.

6

Thanks!! Perderabo for clarify me this question, and Thanks!! to Andrek and Raghu for the solutions.