How to run grep and show x number of lines before and after the match

grep returns just the line where it matched the regex and often what I want to really see is a few (say 2) lines above and below the matched one.
Is there a simple way to achieve it?

EDIT:
OS: Ubuntu based Bodhi Linux.
As mentioned in comments, -C does not work in vanilla but its GNU grep in my case.

Answers:

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Method 1

From man grep:

Context Line Control

-A NUM, –after-context=NUM

Print NUM lines of trailing context after matching lines. Places a
line containing a group separator (–) between contiguous groups
of matches. With the -o or –only-matching option, this has no effect
and a warning is given.

-B NUM, –before-context=NUM

Print NUM lines of leading context before matching lines. Places a
line containing a group separator (–) between contiguous groups
of matches. With the -o or –only-matching option, this has no effect
and a warning is given.

-C NUM, -NUM, –context=NUM

Print NUM lines of output context. Places a line containing a group
separator (–) between contiguous groups of matches. With the -o or
–only-matching option, this has no effect and a warning is given.

See how easy that was? man is your friend.

Method 2

Using awk (more portable) :

awk '
    {
        arr[NR]=$0
    }
    END{
        for (i=0;i<=NR;i++) {
            if (arr[i] ~ grep){
                for (j=i-count; j<=i+count; j++) {
                    print arr[j]
                }
            }
        }
    }
' grep=kdm count=4 /etc/passwd

I grep user kdm againts /etc/passwd with 4 lines before/after the match

In a sh script :

#!/bin/sh

awk '
    {
        arr[NR]=$0
    }
    END{
        for (i=0;i<=NR;i++) {
            if (arr[i] ~ grep){
                for (j=i-count; j<=i+count; j++) {
                    print arr[j]
                }
            }
        }
    }
' grep="$1" count="$2" "$3"

Usage :

./contextgrep <pattern> <count> <file>

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0