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Old 07-10-2010, 11:05 AM   #1
andiramesh_m
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Question Perl command to replace string by line numbe


Hi,
I want to know the Perl command to replace a string by pointing the line number. I know how to replace a string without pointing a line number but I am in need to replace only the two matching string in a file. Any help is appreciated.

Thanks
 
Old 07-11-2010, 04:49 AM   #2
David the H.
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I'm not sure what "pointing to" means here, but if I'm reading correctly, you want to replace a text string with the current line number?

I don't know about perl, but it's simple to do in (gnu) awk.
Code:
awk 'gsub(/string/,NR)1' filename
 
Old 07-11-2010, 05:02 AM   #3
syg00
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Maybe it's just me, but that as a first post, seems like homework.
 
Old 07-13-2010, 11:06 PM   #4
andiramesh_m
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David,
Thanks for your help.

I am looking for a equivalent perl command like the below sed command.

eg:
sed '100s/error/debug/g' <file name>

(This will replace the word "error" to "debug" at line number 100).

Similarly what is the perl command to replace a string available at x line number?

Sed command would not modify the existing file rather we should redirect it to a new file but perl would directly modify the existing file
 
Old 07-13-2010, 11:08 PM   #5
andiramesh_m
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David,
Thanks for your help.

I am looking for a equivalent perl command like the below sed command.

eg:
sed '100s/error/debug/g' <file name>

(This will replace the word "error" to "debug" at line number 100).

Similarly what is the perl command to replace a string available at x line number?

Sed command would not modify the existing file rather we should redirect it to a new file but perl would directly modify the existing file
 
Old 07-14-2010, 04:12 AM   #6
vigilandy
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perhaps you need to look at the -i option for sed.
 
Old 07-15-2010, 12:00 PM   #7
David the H.
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I know hardly anything about perl syntax, but after a quick google search and a couple of minutes on this site, I got this to work:
Code:
perl -i -ple 's/error/debug/g if $. == 100; close ARGV if eof' file
Apparently the last part is only necessary if you're processing multiple files, as you need to reset the $. count for each new file.

There are also examples there on using ranges and how to exclude lines. Check it out.
 
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