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
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.
ReplyDeletegrep -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.
-A and -B will work, as will -C n (for n lines of context), or just -n (for n lines of context).
ReplyDeleteAck works with similar arguments than grep, and accept -C. But it's usually better for searching through code.
ReplyDeleteI normally use
ReplyDeletegrep 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
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
ReplyDeleteawk can do this:
awk '/search_pattern/,0' filename
grep astring myfile -A 5 -B 5
ReplyDeleteThat will grep "myfile" for "astring", and show 5 lines before and after each match
I keep a copy of Brendan Gregg's perl script around for this purpose. Works well.
ReplyDelete