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What's the Diff Between These Two Regexes?

 
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# 8  
Old 06-11-2012
See 'Mastering Regular Expressions' J Friedl

There are different regex engines, and modalities. It is a pain in the butt if you don't know what works with what regex engine. Book lists grep, egrep, perl, etc. and has a tables of these things.

A universal standard is not possible, AFAIK, at this time.
# 9  
Old 06-11-2012
Quote:
Originally Posted by sudon't
It even turns out that there are different greps, who behave differently!
If it helps, these days you only need to know grep. egrep is equivalent to grep -E and fgrep is equivalent to grep -F.

Quote:
Originally Posted by sudon't
A lifetime of Mac OS use has not prepared me for unix.
That made me laugh aloud. Thank you. Smilie

Regards,
Alister
This User Gave Thanks to alister For This Post:
sudon't
# 10  
Old 06-11-2012
Quote:
Originally Posted by jim mcnamara
See 'Mastering Regular Expressions' J Friedl

There are different regex engines, and modalities. It is a pain in the butt if you don't know what works with what regex engine. Book lists grep, egrep, perl, etc. and has a tables of these things.

A universal standard is not possible, AFAIK, at this time.
That's actually the book I got the example from. It's not always clear - at least to me - which standard is being referred to in all examples. I suppose that will come... Standards are possible, of course - you just gotta get people to adopt 'em. ; )

---------- Post updated at 12:56 PM ---------- Previous update was at 12:38 PM ----------

Quote:
Originally Posted by alister
If it helps, these days you only need to know grep. egrep is equivalent to grep -E and fgrep is equivalent to grep -F.


That made me laugh aloud. Thank you. Smilie

Regards,
Alister
Glad I can contribute something to this forum. ; )

But it turns out that GNU grep is different from the grep you get in a standard unix installation. As you might imagine, it took me a while to figure out why certain examples - which I copied very carefully - still wouldn't work. But I serendipitously ran across that info reading about something else.
I am having the same problem now with perl - but that's another thread for another day!
# 11  
Old 06-11-2012
Quote:
Originally Posted by sudon't
But it turns out that GNU grep is different from the grep you get in a standard unix installation. As you might imagine, it took me a while to figure out why certain examples - which I copied very carefully - still wouldn't work. But I serendipitously ran across that info reading about something else.
I am having the same problem now with perl - but that's another thread for another day!
Yeah, different greps support varying extensions to the few options defined by the standard. The GNU tools in particular have a lot of extensions. I would suggest using the opengroup's man pages when learning, if you're interested in being aware of what's an extension to the standard and may or may not be supported by most implementations.

Utilities

Regards,
Alister
This User Gave Thanks to alister For This Post:
sudon't
# 12  
Old 06-11-2012
Quote:
Originally Posted by alister
Yeah, different greps support varying extensions to the few options defined by the standard. The GNU tools in particular have a lot of extensions. I would suggest using the opengroup's man pages when learning, if you're interested in being aware of what's an extension to the standard and may or may not be supported by most implementations.

Utilities
Thanks, that is helpful!
 
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