Grepping a list of words
olli at lurza.secnetix.de
Thu Aug 12 16:44:59 UTC 2010
John Levine <johnl at iecc.com> wrote:
> > > % egrep 'word1|word2|word3|...|wordn' filename.txt
> > Thanks for the replies. This suggestion won't do the job as the list of
> > words is very long, maybe 50-60. This is why I asked how to place them all
> > in a file. One reply dealt with using a file with egrep. I'll try that.
> Gee, 50 words, that's about a 300 character pattern, that's not a problem
> for any shell or version of grep I know.
> But reading the words from a file is equivalent and as you note most
> likely easier to do.
The question is what is more efficient. This might be
important if that kind of grep command is run very often
by a script, or if it's run on very large files.
My guess is that one large regular expression is more
efficient than many small ones. But I haven't done real
benchmarks to prove this.
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