grep a file, but show several surrounding lines?

3608

I would like to grep for a string, but also show the preceding five lines and the following five lines as well as the matched line. How would I be able to do this?

This question is tagged with search logging grep command-line-interface

~ Asked on 2008-08-12 17:55:32

14 Answers


4799

For BSD or 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 number 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.

~ Answered on 2008-08-12 17:57:43


621

-A and -B will work, as will -C n (for n lines of context), or just -n (for n lines of context... as long as n is 1 to 9).

~ Answered on 2008-08-12 17:59:56


78

ack works with similar arguments as grep, and accepts -C. But it's usually better for searching through code.

~ Answered on 2008-09-07 11:13:11


40

grep astring myfile -A 5 -B 5

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

~ Answered on 2008-08-12 17:58:00


20

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

~ Answered on 2008-08-12 18:42:49


16

Use grep

$ grep --help | grep -i context
Context control:
  -B, --before-context=NUM  print NUM lines of leading context
  -A, --after-context=NUM   print NUM lines of trailing context
  -C, --context=NUM         print NUM lines of output context
  -NUM                      same as --context=NUM

~ Answered on 2018-01-12 11:25:38


12

Search for "17655" in "/some/file.txt" showing 10 lines context before and after (using Awk), output preceded with line number followed by a colon. Use this on Solaris when 'grep' does not support the "-[ACB]" options.

awk '

/17655/ {
        for (i = (b + 1) % 10; i != b; i = (i + 1) % 10) {
                print before[i]
        }
        print (NR ":" ($0))
        a = 10
}

a-- > 0 {
        print (NR ":" ($0))
}

{
        before[b] = (NR ":" ($0))
        b = (b + 1) % 10
}' /some/file.txt;

~ Answered on 2013-10-08 00:21:17


10

ripgrep

If you care about the performance, use ripgrep which has similar syntax to grep, e.g.

rg -C5 "pattern" .

-C, --context NUM - Show NUM lines before and after each match.

There are also parameters such as -A/--after-context and -B/--before-context.

The tool is built on top of Rust's regex engine which makes it very efficient on the large data.

~ Answered on 2018-04-11 10:28:35


5

Here is the @Ygor solution in awk

awk 'c-->0;$0~s{if(b)for(c=b+1;c>1;c--)print r[(NR-c+1)%b];print;c=a}b{r[NR%b]=$0}' b=3 a=3 s="pattern" myfile

Note: Replace a and b variables with number of lines before and after.

It's especially useful for system which doesn't support grep's -A, -B and -C parameters.

~ Answered on 2018-04-11 10:24:12


4

$ grep thestring thefile -5

-5 gets you 5 lines above and below the match 'thestring' is equivalent to -C 5 or -A 5 -B 5.

~ Answered on 2019-01-05 18:39:36


4

Grep has an option called Context Line Control, you can use the --context in that, simply,

| grep -C 5

or

| grep -5

Should do the trick

~ Answered on 2019-03-11 07:11:40


1

You can use option -A (after) and -B (before) in your grep command try grep -nri -A 5 -B 5 .

~ Answered on 2020-12-30 09:41:18


1

If you search code often, AG the silver searcher is much more efficient (ie faster) than grep.

You show context lines by using -C option.

Eg:

ag -C 3 "foo" myFile

line 1
line 2
line 3
line that has "foo"
line 5
line 6
line 7

~ Answered on 2020-04-28 17:14:25


1

I use to do the compact way

grep -5 string file

That is the equivalent of

grep -A 5 -B 5 string file

~ Answered on 2019-12-11 17:24:10


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