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grep a file, but show several surrounding lines?

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By User


I would like to grep for a string, but show the preceding 5 lines and following 5 lines as well as the matched line. I'm scanning for errors in a logfile, and want to see the context.



Any clues for the clueless?


Source: Tips4all, CCNA FINAL EXAM
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  1. UserMay 17, 2012 at 11:09 AM

    For GNU grep you can use -B num to set how many lines before the match and -A num for the number of lines after the match.

    grep -B 3 -A 2 foo README.txt

    If you want the same amount of lines before and after you can use -C num.

    grep -C 3 foo README.txt

    This will show 3 lines before and 3 lines after.

    ReplyDelete
  2. UserMay 17, 2012 at 11:09 AM

    -A and -B will work, as will -C n (for n lines of context), or just -n (for n lines of context).

    ReplyDelete
  3. UserMay 17, 2012 at 11:09 AM

    Ack works with similar arguments than grep, and accept -C. But it's usually better for searching through code.

    ReplyDelete
  4. UserMay 17, 2012 at 11:09 AM

    I normally use

    grep searchstring file -C n # n for number of lines of context up and down


    Many of the tools like grep also have really great man files too. I find myself referring to grep's man page a lot because there is so much you can do with it.

    man grep


    Many GNU tools also have an info page that may have more useful information in addition to the man page.

    info grep

    ReplyDelete
  5. UserMay 17, 2012 at 11:09 AM

    Ok, but what if want to show all lines of output after the match? grep -A0 and grep -A-1 don't cut it... – Noah Jul 22 at 2:18


    awk can do this:

    awk '/search_pattern/,0' filename

    ReplyDelete
  6. UserMay 17, 2012 at 11:09 AM

    grep astring myfile -A 5 -B 5


    That will grep "myfile" for "astring", and show 5 lines before and after each match

    ReplyDelete
  7. UserMay 17, 2012 at 11:09 AM

    I keep a copy of Brendan Gregg's perl script around for this purpose. Works well.

    ReplyDelete

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