Sunday, May 8, 2011

Awk - replace n-th occurrence of pattern


Input file:
$ cat file.txt
FR 24
AA 33
EE 34
EE 46
BE 30
AA 31
DE 90
AL 10
AA 50
FR 67
EE 94
AA 80

Required:
Replace the "third" occurrence of first field "AA" with text "XX" in the above file.

Awk Solutions:
$ awk '$1=="AA" {
count++
if(count == 3){
sub("AA","XX",$1)
}
}
{print}' file.txt

Output:
FR 24
AA 33
EE 34
EE 46
BE 30
AA 31
DE 90
AL 10
XX 50
FR 67
EE 94
AA 80

In-case you want to add 100 to the 2nd field of that line where first field "AA" has occurred for the 3rd time, here is a way:
$ awk '$1=="AA" {
count++
if(count == 3){
$2=$2+100
}
}
{print}' file.txt

Output:
FR 24
AA 33
EE 34
EE 46
BE 30
AA 31
DE 90
AL 10
AA 150
FR 67
EE 94
AA 80

Related posts:
- Print up-to nth occurrence of a pattern in a file using awk
- Replace field other than the first occurrence using awk
- Awk print first occurrence of a set in a file

2 comments:

Malik said...

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Akhil said...

Nice article.
Examples of Awk command in unix

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