Strings replacement help needed

[Md.Shahabuddin]

Hi,

I have to replace a string in a file of 1000 lines. That string is distributed and i want to replace only 200 lines out of 1000 lines of that particular strings.

It should be in interactive mode where i can get the information before replacing that string.

Thanks in advance.
Waiting for the earliset response.

[James R. Ferguson · Accepted solution]

Hi:

Try this:

# perl -pe 'if ($n<200) {$n++ if s/XX/YY/g}' file

Change "XX" and "YY" to the patterns you need.

Regards!

...JRF...

[OldSchool]

I believe the perl above is going to change the first 200 occurrances, while the request seems to be for 200 out of 1000, and he need to inspect it before commiting the change.

in this case I'd use vi.

to search:
/ where is the old text
then "n" to locate the next occurance

method of replacement is going to vary depending on if its a 'word', or exactly the same length or buried in some longer string...

insuffficient information for a complete answer.

[James R. Ferguson]

Hi (again):

The Perl script I suggested replaces up to 200-lines regardless of how many matches occur per line.

It is trivial to modify the substitution to "words" or simply any string sequence as I used.

I agree that more information would lead to a more complete answer.

...JRF...

[Md.Shahabuddin]

James.....

Thank you so much. Its working.

[OldSchool]

JRF: I read this "It should be in interactive mode where i can get the information before replacing that string."

as "I need to see it in context before confirming change"...which apparently isn't the case

[Md.Shahabuddin]

U are right James.

can it be done in interactive mode?
Do u have any alternatives?

[James R. Ferguson]

Hi (again):

No, I made no provisions for doing this "interactively". I find it hard to imagine why you want to replace 200 of 1000 lines "interactively", which to me suggests confimation as you proceed. If this is true, do you count a line toward the "200" if you reject its change or only if you accept it?

Since I left the input file un-modified, I felt that this was an adequate "interactive" preview step in and of itself. Re-running the script after inspecting the results would then only require a simple redirection to a new output file or the change of the Perl swithes from '-pe' to '-pi -e' to affect an in-place update.

I interpreted your original question to mean _lines_ on which substitutions occur regardless of how many _times_ per line a substitution was made. How would that factor into your count toward "200" if you were to ask for confirmation at each step?

What is the problem you really want to solve? If it isn't an on-going one, using 'vi' as Oldschool suggested might be the fastest solution.

Regards!

...JRF...

[Arturo Galbiati]

Hi,
I have to use VI and a lot of patience.
Find the string (/) and replace it (r), find next occurrence (n) and replace it (.) and so on.

HTH,
Art

[Dennis Handly]

>Art: Find the string (/) and replace it (r), find next occurrence (n) and replace it (.)

You can also use:
:first,last s/string1/string2/gc

The "c" asks you to confirm for each line.