a scripting question

[Curtis Larson_1]

how do you parmaterize the pattern in a case statement for sh or ksh. ie:

#!yourshell
pattern="ab|bb"
c="ab"
case $c in
$pattern) print $c;;
ab) print here;;
*) print "not found";;
esac

sh or ksh will return "here". how do I code this example to return "ab", which is what it does when using the /usr/dt/bin/dtksh shell.

[Sridhar Bhaskarla]

Hi Curtis,

I can think of one work around it works for you.

#!/usr/bin/ksh
pattern="ab|bb"
c="ab"
cat << EOF > /tmp/sh$$
case $c in
$pattern ) print $c;;
ab) print here;;
*) print "not found";;
esac

EOF

ksh /tmp/sh$$
rm /tmp/sh$$

-Sri

[Bernie Vande Griend]

Sridhar idea would work and it also shows why this doesn't ordinarily work. That's because in ksh and sh, you can't use a variable to substitute a pattern match. It will just try to pattern match the literal 'ab|bb', instead of substituting and then trying to use the logic within. This also happens if you try to do this same thing with arrays. I don't believe there's any way around this other than causing it to be evaluated twice like Sridhar does.

[Rodney Hills]

Perl offers that ability. Although it has no case statement, you can do the following-

$regexp="ab|b";
...
if (/$regexp/) {
...
}

Within ksh you might be able to use the "eval" shell command (if it is a small list of case statements). eg-
x="ab|b"
val="b"
eval "case $val in $x) echo yes;; *) echo no;; esac"

-- Rod Hills

[Marco Paganini]

Hello Curtis,

This workaround should work (without intermediate files)

#!/bin/sh

pattern="ab|bb"
c="ab"
eval "case $c in
$pattern) print $c;;
ab) print here;;
*) echo \"not found\";;
esac"

Regards,
Paga

[Curtis Larson_1]

thanks everyone for your suggestions

i believe using the eval within the if-then-else construct to more useable for my programming.

if eval [[ $c = @($pattern) ]] ;then
print $c
elif eval [[ $c = "ab" ]] ;then
print here
else
print "not found"
fi

[Sridhar Bhaskarla]

Interesting thing about the way you assigned points. I honor your judgement of giving me 3 points as this solution will not suit to your needs.

However, it would have been nice if you had given your program completely so that we might have suggested to use if-then-else construct instead of wasting our time to think about a workaround.

We only can think about the solutions based on the information you gave.

-Sri