Super User is a question and answer site for computer enthusiasts and power users. It's 100% free, no registration required.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I am very new to shell scripting I had a small query regarding the file parsing.

So, here's what I am trying to do:
I run an svn merge command, and genaratea conflict file my conflict file is stored as conflicts.txt

What I want to do is read this file line by line and parse one line to match against some keywords.

For example one of the line in files look like this:
C Client/Game/src/test/test.php

Now I want to parse this line and search for the keyword test, in case I find it I want to do some action on it, for example aborting with exit status 2, 3, etc..

for example i want to iterate throught a text file called "FILENAME" which looks like this

30 '!' C Client/test.js

31 '!' C Client/test2.js

32 '!' C Client/test3.js `

what i am doing is catting the file using the while loop and cat commnad

cat $FILENAME | while read LINE do echo $LINE done

here i am just printing the line , i want to know how can i search for a keyworkd in the line and if i find that keyword how can i do some action on it like exiting with status 1

Can you please suggest some way to do this..

share|improve this question
I'm not quite sure what you're trying to do, but as it sounds, everything you need is already there. Check out the tool grep. – SBI Jun 12 '13 at 15:30
PLease include some specific examples. Show us your input file and your expected output. Do you have one keyword or many? – terdon Jun 12 '13 at 15:39
@terdon i have edited my question – Riddle Jun 12 '13 at 16:38

There are many ways of doing this, depending on your needs.

  1. Simply print all lines containing the keyword test:

    grep test file.txt
  2. The same but for many keywords. Create a file that has all the keywords, one per line and run

    grep -f keywords.txt file.txt
  3. Process a file line by line, exit if the line is found

    while read line; do echo $line | grep test && break; done < file.txt
  4. Exit with status 1 if the line matches. Unfortunately,if I remember correctly (not 100% sure), bash only allows you to set return values in functions. So, to get an exit status you need to use something else. Perl for example:

    perl -ne '/test/ && exit(1)' file.txt
  5. Though you can't set an exit value, you can still do something similar with bash. The exit value of the last command run is always saved as $? in bash, that means you can test the value of $? and act accordingly:

    while read line; do let c++; echo $line | grep test >/dev/null; 
      if [[ $? == 0 ]] ; then echo Match for line $c : $line;
      else echo No match for line $c; fi  
    done < file.txt 
share|improve this answer

Simplest way is not to parse file line-by-line at all.

grep -q 'keyphrase' filename && exit <exitcode> 
share|improve this answer
Don't work as root in the shell just to grep a string from a file. – ott-- Jun 12 '13 at 17:10
I don't deal with formatting yet :) – madlynx Jun 12 '13 at 17:16
$ function some_action { 
    echo found keyword

$ if grep -q -m1 -e 'test3' < input;
found keyword

grep options:

  • -q: quiet; don't print matches
  • -m1: exit after one match
  • -e: expression (keyword)


$ grep . input
30 '!' C Client/test.js
31 '!' C Client/test2.js
32 '!' C Client/test3.js

$ if grep -q -m1 -e 'test3' < input; then some_action ; fi
found keyword
share|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.