replacing according to position

[Reen]

Hi all,
can anybody help in this
In a line, i have a pattern tat is to be replaced.

using sed , i can replace in a particular line, but tat pattern can occur in the line in many other places.
i want only one instance to be replaced.

[Reen]

Attached is the file.
I want the 2nd instance of Blore to b replaced in 2nd line.
But in the actual file am not sure of the occurance of this instance.It can be 3rd instance.
But the position is fixed.
so in this case, 23-27 characters in 2nd line to be replaced by Mlore

[Dennis Handly]

>using sed, i can replace in a particular line, but that pattern can occur in the line in many other places. i want only one instance to be replaced.

One instance per line, or one per whole file?
For the former, don't add "g" to the "s" function, then it only will replace one.

If it is once per file, you'll need to write an awk script. To replace to the first then copy the rest of the file.

[Reen]

Thanks Dennis.
Can u give me a solution for my attached file

[Yogeeraj_1]

hi Reen@,

In the vi editor, can you try this:
:1,$s/.Blore/Mlore

kind regards
yogeeraj

[Dennis Handly]

>Yogeeraj: 1,$s/.Blore/Mlore

You may need to quote the "." otherwise it would match the first:
:1,$s/\.Blore/Mlore

(But I guess it was safe since there are no chars before the first Blore.)

>But the position is fixed. so in this case, 23-27 characters in 2nd line to be replaced by Mlore

That makes it easy:
sed -e 's/^\(......................\)Blore/\1Mlore/'

(There should be 22 dots. The \1 puts them back into the output. If only one the second line, you can use '2s/'.)

[James R. Ferguson · Accepted solution]

Hi:

A bit more readable (and much easier to maintain) is the specificatino of the number of character repetitions, thusly:

# sed -e 's/^\(.\{22\}\)Blore/\1Mlore/'

Note that the curly braces must be escaped with a backslash just like the parentheses must be.

Regards!

...JRF...

[Reen]

Hi all,
Thanks a lot for the help.
One more query is that,
is ther any restriction on the no. of characters?
I mean.. in a line can i change the 260-264th character in the similar manner?
I hav to achieve that.

[Dennis Handly]

>is there any restriction on the no. of characters?

No, you can use JRF's improvement, and you just type in the number.
^\(.\{259\}\)

[Reen]

Dennis,
Didnt get JRF`s improvement???