substitution question in perl

sharky · 11-03-2008, 11:32 AM

Let's say I have a line of text as follows;

"_sometext/somemore_text/abc>, Output File <some_more_text "

Using perl I want to remove "Output File" and everything that follows. I have tried 's/Output File*//g' without success. It only removed 'Output File' and left all following text as is.

I thought * meant 'everything that follows. Apparently I was wrong. Any comments advice or suggestions is welcome.

thanks,

Sergei Steshenko · 11-03-2008, 12:15 PM

Quote:

Originally Posted by sharky

Let's say I have a line of text as follows;

"_sometext/somemore_text/abc>, Output File <some_more_text "

Using perl I want to remove "Output File" and everything that follows. I have tried 's/Output File*//g' without success. It only removed 'Output File' and left all following text as is.

I thought * meant 'everything that follows. Apparently I was wrong. Any comments advice or suggestions is welcome.

thanks,

s/\bOutput\s+File.*//

jan61 · 11-03-2008, 12:17 PM

Moin,

the "*" in Perl says: the previous character or expression 0 .. n times. So if you want to remove everything from "Output File" to the end of line you have to use: "s/Output File.*//" - the "." is the expression for any character.

Jan

sharky · 11-03-2008, 03:09 PM

Thanks. It was the "." culprit.

sundialsvcs · 11-03-2008, 07:10 PM

"At first blush," it seems to me that you were hoping that the semantics of the ls command would somehow work here.

Nope. Sorry.

When you're contemplating any situation where (you know...) "a regular expression will really help me here," bear in mind that there are two things which regex-based logic fundamentally needs to know:

"What place-markers will tell me that 'I am in the right neighborhood(s)?'"
(Then... "now that I'm here...") "What will identify 'what I need to isolate?, perchance to change?'"