substitute a pattern only if some other pattern is present

raghu123 · 06-26-2009, 05:51 AM

Hi all

I have this file
sandy is a writer
writer is a poet
sandy is a poet

i want the O/P to be

sandy was a writer
writer is a sandy
sandy was a poet

MEANS, wherever "sandy" is there, I want 'is' to be replaced by 'was'
please help

ghostdog74 · 06-26-2009, 06:17 AM

where is your code?

vonbiber · 06-26-2009, 06:32 AM

Quote:

Originally Posted by raghu123

Hi all

I have this file
sandy is a writer
writer is a poet
sandy is a poet

i want the O/P to be

sandy was a writer
writer is a sandy
sandy was a poet

MEANS, wherever "sandy" is there, I want 'is' to be replaced by 'was'
please help

you want to replace 'is' by was whenever it is
preceded by 'sandy' or writer.

you can do this with sed:

suppose the original file is input.txt
you can get a resulting file named output.txt by:

# sed 's/\(sandy \|writer \)is /\1was /g' input.txt > output.txt

Telemachos · 06-26-2009, 06:53 AM

@Vonbiber: No, I think that the OP wants to change 'is' to 'was' only when the initial name is 'sandy'. (Perhaps sandy has passed away?)

If that's right, here's how I would do it using Perl:

Code:

perl -i.bak -ple 's/is/was/ if m/^sandy/' filename.txt

Replace 'filename.txt' with the name of your file. That should make the changes and save a backup as filename.bak.