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.

Answer 1

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

Answer 2

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

Answer 3

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)'