July 22, 2004

pcregrep VS grep::[Misc]

since grep can't support binary or extend-coding, I change most of my scripts to pcregrep.
To my surprise, the script runing much faster after I switch to pcregrep:

Here is a example:

mcfarm:~/work/rootfit/background-only-step1/output$ time pcregrep 1000 exper.1.data > /dev/null
0.940u 0.030s 0:00.97 100.0% 0+0k 0+0io 103pf+0w
mcfarm:~/work/rootfit/background-only-step1/output$ time grep 1000 exper.1.data > /dev/null
28.350u 0.470s 0:29.45 97.8% 0+0k 0+0io 155pf+0w

0.94 VS 28.35 !!!

Generally say, pcregrep is more than 20 times faster then grep.

pcregrep searches files for character patterns, in the same way as other grep commands do, but it uses
the PCRE regular expression library to support patterns that are compatible with the regular expressions
of Perl 5. See pcre(3) for a full description of syntax and semantics.

If no files are specified, pcregrep reads the standard input. By default, each line that matches the pat-
tern is copied to the standard output, and if there is more than one file, the file name is printed
before each line of output. However, there are options that can change how pcregrep behaves.

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