Extract one word after a specific word on the same line

Question

How can I extract a word that comes after a specific word in Linux (csh)? More precisely, I have a file which has a single line which looks like this:

[some useless data] --pe_cnt 100 --rd_cnt 1000 [some more data]

I want to extract the number 100 which is after the --pe_cnt word. I cannot use sed as that works only if you want to extract an entire line. Maybe I can use awk?

Also, I have multiple files that have different values instead of 100 so I need something that extracts the value but doesn't depend on the value.

"awk" is one possibility. For example, `echo 5 4 | awk '{ print $2 }' ` should display "4". — paulsm4, Jun 28 '13 at 18:21

jaypal singh · Accepted Answer · 2013-06-28T18:29:30.633

34

With awk:

awk '{for(i=1;i<=NF;i++) if ($i=="--pe_cnt") print $(i+1)}' inputFile

Basically loop over each word of the line. When you find the first you are looking for, grab the next word and print it.

With grep:

grep -oP "(?<=--pe_cnt )[^ ]+" inputFile

edited Jun 28 '13 at 18:29

answered Jun 28 '13 at 18:23

jaypal singh

74,723
23
102
147

1

You need to add a space at the end of the lookbehind pattern in grep. – ctn Jun 28 '13 at 18:28
Yep sorry didn't test it. Thank you! :) – jaypal singh Jun 28 '13 at 18:29
N.B. `grep` on Mac OSX 10.8 doesn't have `-P`. – Kevin Jun 28 '13 at 18:30
JS웃: Thanks a lot for the quick reply. The first command worked perfectly! The second command did not give any output though. – Rahul Jun 28 '13 at 18:30
@Rahul Sorry I had missed a space in the look behind which was corrected by ctn. It should work now. – jaypal singh Jun 28 '13 at 18:33
Works great! But can you explain the `grep` regexp, in particular what `(?<=--pe_cnt )` does? – Andres F. Oct 17 '14 at 15:24
Nevermind, it's a perl regexp using look around assertions, [as I found here](http://perldoc.perl.org/perlre.html). – Andres F. Oct 17 '14 at 15:27
The `sed` answer is more efficient and more idiomatic than this answer, and should probably be the most upvoted, if not the accepted answer. – tripleee Jul 13 '16 at 14:03
1

your answer helped me a lot. Thank you – Ashwaq Apr 09 '19 at 10:39

ctn · Answer 2 · 2013-06-28T18:27:24.407

6

You can use sed. Just make a group of want you want to match and replace the whole line with the group:

sed -n 's/^.*pe_cnt\s\+\([0-9]\+\).*$/\1/p' file

edited Jun 28 '13 at 18:27

answered Jun 28 '13 at 18:21

ctn

2,887
13
23

There was an error in the pattern previously but it's fixed now. – ctn Jun 28 '13 at 18:40

score 1 · Answer 3 · answered Jun 28 '13 at 18:29

1

If there is a single-space character between --pe_cnt and 100, you may be able to use lookahead and lookbehind assertions

grep -oP '(?<=--pe_cnt\s)\d+(?=\s+--rd_cnt)'

answered Jun 28 '13 at 18:29

iruvar

22,736
7
53
82

Probably don't even need the `--rd_cnt`, it doesn't necessarily matter what the following options are – Kevin Jun 28 '13 at 18:31
Ok. Thanks for the tip. I'm a newbie to Linux so these tips help a lot. – Rahul Jun 28 '13 at 18:39

score 0 · Answer 4 · answered Mar 05 '21 at 09:42

0

This may be the shortest version:

grep -oP 'pe_cnt \K[^ ]+' file

answered Mar 05 '21 at 09:42

Jotne

40,548
12
51
55

Extract one word after a specific word on the same line

4 Answers4

Linked

Related