Bash: Assigning a substring to a variable

[sean]

I've been learning bash scripting, but unfortunately it's more out of necessity than taking my time and learning the meaning of all the syntax really well. I've run into a problem that I can't seem to figure out from any documentation - so if anyone can shed some light on this I'd be appreciative.

I have a loop where I need to loop through all the files, and do several different things with the part of the filename before the extension. The first 'echo' statement below outputs exactly what I need, however since I do several different actions with that output, I really need it to be stored in it's own variable.

for file in `ls *.txt `
do
	# outputs the desired result, but I need it in a variable
	echo `expr "$file" : '\([^.]\+\)'`

	# this either tries to execute the result or yields a '0'
	let s=`expr "$file" : '\([^.]\+\)'`
	echo $s
done

My first thought was the 'let' and the second echo, but that results in a '0'. I've also tried wrapping the expression in a $( ... ) but that yields '0' if I remove the back ticks, and tries to execute the result as a command if I leave the backticks. I also initially thought that having slashes in the file path was causing it to be evaluated differently, but I modified the program so there are no longer any slashes in the path - just the filename.

Any thoughts?

[Ronix]

You should be able to assign the first expression you're echoing to a variable:

for file in `ls *.txt `; do
    x=`expr "$file" : '\([^.]\+\)'`
    echo $x
done

[sean]

Well what'd'ya know, that worked! I knew I was missing the point of something, but I wouldn't have thought it would be something as simple as the real meaning of 'let'. Thanks!