replace specific character after specific line by awk

Syed Tarique Moin · 07-19-2010, 11:33 AM

Hello,

I want to replace specific character in a file after every specific line.

example as follows.

O 000000000000000000
A 111111111111111111
C 222222222222222222
D 333333333333333333
O 000000000000000000
A 111111111111111111
C 222222222222222222
D 333333333333333333

I want to replace only O with T after specific interval starting from line 1 as can be seen from here. I would be highly grateful for the valuable suggestion or the way how to do this.

Regards

pixellany · 07-19-2010, 11:48 AM

Looking at your example, we could guess that the code could match a string of zeros, or simply "O" at the beginning, or Line numbers 1,5,9,13...etc.

Here's three solutions---one for each option:

Code:

sed '/0000000/s/O/T' filename > newfilename

sed 's/^O/T/' filename > newfilename

sed '1,+4s/^O/T/' filename > newfilename

ghostdog74 · 07-19-2010, 01:47 PM

Code:

awk '$1=="O"{$1="T"}1' file