How do I parse a line thorugh a file in bash

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..

3

3 Answers

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 

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

grep -q 'keyphrase' filename && exit <exitcode> 

2

$ function some_action { echo found keyword
}
$ if grep -q -m1 -e 'test3' < input; then some_action fi
found keyword

grep options:

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

e.g:

$ 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

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