Shell Programming and Scripting

Hi. I want to be able to update only one line in a file that matches a key using sed, but I can't seem to get this (the key is right at the beginning of each row)

Here is what I have tried so far, but every row is being updated. I want the end result to be that the input file only has the single matching record updated, and nothing else:

grep ^$1 input.txt | sed s/$OLD/$NEW/1 < input.txt > input.txt

BTW - I do not want this:

grep ^$1 input.txt | sed s/$OLD/$NEW/1

I want the rest of the unmodified records in the result also. That's why I am trying to pipe the entire input file to sed, and I was hoping that grep would locate the record to modify.

Thanks.

Brendan

Can you provide and example of the input file and the resulted desire file?

Input file:

01:15
02:30
03:19
04:50
05:65
06:05

Output file:

01:15
02:30
03:27
04:50
05:65
06:05


How would I write a sed command to update 03:19 to 03:27 without
modifying the other records? Key = first two bytes of each row.

Thanks!

Code:

sed '/^03/s/19/27/' input.txt

That works great, thanks so much!!

If I may ask - I know the ^ means the beginning of a row, but what exactly does the /^03 mean to the sed command when it preceeds the s/ ?

Thanks again!!

Brendan

The command reads:
"for lines that start with the characters 03, substitute the first instance of 19 with 27"

Nice... THANK YOU! You really helped me out.

All the best.

Brendan