Grepping a list of words
Oliver Fromme
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.
Best regards
Oliver
--
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
FreeBSD-Dienstleistungen, -Produkte und mehr: http://www.secnetix.de/bsd
"To this day, many C programmers believe that 'strong typing'
just means pounding extra hard on the keyboard."
-- Peter van der Linden
More information about the freebsd-questions
mailing list