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Chopping off the last field of each line?

I'm working on the Web site for Creating Cool Web Sites and just realized that the little Unix trick I used while editing a file is actually a beautiful example of why so many people love Unix so much, so I thought I'd share it. The problem: a file where lines have 1-10 words + a last field value (in this case, a page number) that I don't want. The challenge is to figure out how to easily remove that last field, when there are a variable number of fields on the line.

Dave's Answer: My first instinct was to turn to awk or perl, but in fact there's a much easier way using basic Unix utilities: rev and cut:

$ rev inputfile | cut -f2- | rev > outputfile

How does this work? The rev command reverses each line of input, so that means that the first field of each now-reversed line is the field that we want to remove. That's easily done with cut with the -f2- flag (that means output field two through the end of the line). Then, finally, we re-reverse (that is, fix) each line and save the output in a new file.

Quickly and easily done.

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Comments

well done

Posted by: pedestrian at August 19, 2007 9:20 AM

try this

awk '{$NF=""; print $0}'

Cheers
Amit

Posted by: Amit at July 7, 2008 12:28 AM

I prefer:

awk '{NF--;print}'

With NF="" you will have additional spaces at the end of each line.

Posted by: porges at March 5, 2009 7:50 AM

Nice, this just solved a problem I've been working on. So thanks.

I figured I'd try to make it work without the rev. Reversing the argument of the -f parameter should returned the same results.

Posted by: Cannon at February 13, 2010 2:07 PM

I have something to say, now that you mention it, but ...

I do have a lot to say, and questions of my own for that matter, but first I'd like to say thank you for all your efforts on this Web site by buying you a cup of coffee!

I do have a comment, now that you mention it!