Grepping a list of words

Oliver Fromme olli at
Thu Aug 12 16:44:59 UTC 2010

John Levine <johnl at> 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.

Best regards

Oliver Fromme, secnetix GmbH & Co. KG, Marktplatz 29, 85567 Grafing b. M.
Handelsregister: Registergericht Muenchen, HRA 74606,  Geschäftsfuehrung:
secnetix Verwaltungsgesellsch. mbH, Handelsregister: Registergericht Mün-
chen, HRB 125758,  Geschäftsführer: Maik Bachmann, Olaf Erb, Ralf Gebhart

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