Testing strings in BASH

[TobyR]

I've read that * is wild card in BASH for one or more characters, and that "=" is a test for the equivalence of strings. I'm trying to test whether $TESTSTRING contains a certain pattern of characters ("abc") and so am using

if [ "$TESTSTRING" = *abc* ]
then
echo "True"
fi

... and am not getting 'True'. What basic error am I making?

thanks.

[asarch]

What about this:

#!/bin/bash

TESTSTRING='justlinuxisthebestplaceabcdefghijkl'

if $( echo $TESTSTRING | grep --quiet 'abc' )
then
echo true 'abc'
fi

if $( echo $TESTSTRING | grep --quiet 'oby' )
then
echo true 'oby'
fi

[TobyR]

Yup, that did it. Many thanks.

[bwkaz]

Originally posted by TobyR
I'm trying to test whether $TESTSTRING contains a certain pattern of characters ("abc") and so am using

if [ "$TESTSTRING" = *abc* ]
then
echo "True"
fi

... and am not getting 'True'. What basic error am I making? You can't do wildcarding with the "[" builtin command (or the "test" builtin, for that matter).

If you want to match a regular expression, then use grep, as asarch did. (But that wastes one or maybe two processes.)

If you only want to match a glob pattern (which seems to be what you're describing), then use case. It's a shell builtin, so you don't waste a process, and if you aren't using the full regular-expression language anyway, then why use it? ;) Anyway, case looks like this:

case "$TESTSTRING" in
*abc*)
echo "True"
;;
*)
echo "False"
;;
esac The string before the ) is checked to see if it's a valid glob match to the "$TESTSTRING" value. If so, then the commands that follow the ) are executed, until the first ;; sequence. Then control skips to the esac.

If the first pattern doesn't match, then the shell skips to the next pattern and tries to evaluate it. (So in effect, a *) pattern means "if nothing else matches, use this".)

[asarch]

You can also do this if you want to emulate

strstr(3) (http://techpubs.sgi.com/library/tpl/cgi-bin/getdoc.cgi?coll=linux&db=man&fname=/usr/share/catman/man3/strstr.3.html&srch=strstr):
#!/bin/bash

TESTSTRING='justlinuxisthebestplaceabcdefghijkl'

function strstr ( )
{
echo $1 | grep --quiet $2
}

if $( strstr $TESTSTRING 'abc' )
then
echo true abc in function strstr
fi

if $( strstr $TESTSTRING 'oby' )
then
echo true oby in function strstr
fi