grep to find "print" not "#print"

Question

In debugging, I use a lot of 'print' and commenting out it with '#print'. How can I use grep to find the line without '#' before 'print'?

# print <- not detect
#print <- not detect
abc # print <-- not detect
print <- detect

See How to grep on source code without catching comments and How to grep lines which does not begin with “#” or “;”? first. — manatwork, Mar 13 '13 at 15:28
Should it match print '#';, print ''; # here we print, str='#'; print or str='# print'? There is probably no 100% safe expression without partially rebuilding the language's parser. — manatwork, Mar 13 '13 at 15:38

score 3 · Accepted Answer · answered Mar 13 '13 at 16:41

3

grep '^[^#]*print'

Would be print only preceded by non-# characters.

answered Mar 13 '13 at 16:41

Stéphane Chazelas

544,893

score 1 · Answer 2 · answered Mar 13 '13 at 15:32

1

Classic solution:

grep -v '^#' <input |grep 'print'

answered Mar 13 '13 at 15:32

H.-Dirk Schmitt

2,009

The issue is that # can be anywhere in the line. I updated my post. – prosseek Mar 13 '13 at 15:36
The solution greps for any line without the #, then checks for the word 'print'. – ThaMe90 Mar 13 '13 at 15:38
1

@prosseek Changing the requirements in a question after you receive an answer is not the right way. Better is to ask a new question. Never mind, luckily the solution works also for the changed requirements. But please do not change again the requirements. Ask instead a new question. – H.-Dirk Schmitt Mar 13 '13 at 16:05

score 1 · Answer 3 · answered Mar 13 '13 at 16:07

1

The easiest approach is probably going to be to use two greps, piped together.

$ grep 'print' <input | grep -v '#[[:space:]]*print'

With the file input containing your examples, that gives:

print <- detect

That works for all of your examples. Which is probably good enough, but as manatwork and I point out in comments, its going to be very difficult to defeat all the edge cases with grep.

answered Mar 13 '13 at 16:07

derobert

109,670

For this kind of job, weeding out 80% of the "should not detect" is probably good enough. – vonbrand Mar 13 '13 at 16:27

score 1 · Answer 4 · edited Mar 13 '13 at 16:46

1

I'm still learning but wouldn't the ff work as well?

grep -v '#[ ]*print' input_file

edited Mar 13 '13 at 16:46

Michael Mrozek

93,103
40
240
233

answered Mar 13 '13 at 16:23

morgan_g

61

grep to find "print" not "#print"

4 Answers4