grep: show lines surrounding each match - search

Question

How do I grep and show the preceding and following 5 lines surrounding each matched line?

Answer 1

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.

Answer 2

-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).

Answer 3

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

Answer 4

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

Answer 5

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.

Answer 6

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

Answer 7

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

Answer 8

If you search code often, AG the silver searcher is much more efficient (ie faster) than grep.
You show context lines by using the -C option.
Eg:
ag -C 3 "foo" myFile
line 1
line 2
line 3
line that has "foo"
line 5
line 6
line 7

Answer 9

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;

Answer 10

Let's understand using an example.
We can use grep with options:
-A 5 # this will give you 5 lines after searched string.
-B 5 # this will give you 5 lines before searched string.
-C 5 # this will give you 5 lines before & after searched string
Example.
File.txt contains 6 lines and following are the operations.
[abc#xyz]~/% cat file.txt # print all file data
this is first line
this is 2nd line
this is 3rd line
this is 4th line
this is 5th line
this is 6th line
[abc#xyz]~% grep "3rd" file.txt # we are searching for keyword '3rd' in the file
this is 3rd line
[abc#xyz]~% grep -A 2 "3rd" file.txt # print 2 lines after finding the searched string
this is 3rd line
this is 4th line
this is 5th line
[abc#xyz]~% grep -B 2 "3rd" file.txt # Print 2 lines before the search string.
this is first line
this is 2nd line
this is 3rd line
[abc#xyz]~% grep -C 2 "3rd" file.txt # print 2 line before and 2 line after the searched string
this is first line
this is 2nd line
this is 3rd line
this is 4th line
this is 5th line
Trick to remember options:
-A  → A means "after"
-B  → B means "before"
-C  → C means "in between"

Answer 11

I do it the compact way:
grep -5 string file
That is the equivalent of:
grep -A 5 -B 5 string file

Answer 12

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.

Answer 13

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

Answer 14

$ 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.