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I'm new to Linux. I've a file which contains list of movie names and their release year. I want to list out all release years. Specifically my file looks like below 

TDKR(2012)    
Vicky Cristina Barcelona (2008)  
...

I tried grep with regex as follows

grep "^.*\\([0-9]*\\)$" movie.txt

and it works but it is printing entire line I want only years. Can I do it with grep?

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3 Answers

up vote 3 down vote accepted

GNU grep supports an -o option which will give you the matching pattern, so you could use grep -o '([0-9]\+)' but this will also print the parentheses. For more flexibility and portability, though, you should post-process with sed:

grep '([0-9]\+)$' movie.txt | sed 's/.*(\([0-9]\+\))$/\1/'
# assumes that the year is always at the end of the line.
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Well, grep being a subset of sed, there's no need for grep here (also note that \+ in sed is not portable nor standard). sed -n 's/.*(\([0-9]\{1,\}\)).*/\1/p'. All those assume there's only one occurrence of (xxx) per line. – Stephane Chazelas Oct 22 '12 at 19:09
@sch I don't have it in front of me to test, without grep will this filter out lines that don't match the pattern at all? – Random832 Oct 22 '12 at 20:20
Yes, -n is to not print the line by default, and the p flag to the s command is to print the line when the substitution is successful. – Stephane Chazelas Oct 22 '12 at 21:22
With GNU grep, you can use Perl regex syntax: grep -Po '(?<=\()[0-9]+(?=\))' but it doesn't exactly roll off the tongue. – Gilles Oct 22 '12 at 22:12
up vote 2 down vote

If the numbers are always the last field, then you can do it with a single awk command.

bash$ awk '{gsub(/\(|\)/," "); print $NF};' $file
2012
2008
...
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up vote 2 down vote

With perl:

perl -lne 'print for /\((\d+)\)/g'
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