l i n u x - u s e r s - g r o u p - o f - d a v i s
L U G O D
 
Next Meeting:
November 4: Social gathering
Next Installfest:
TBD
Latest News:
Oct. 10: LUGOD Installfests coming again soon
Page last updated:
2001 Dec 30 17:08

The following is an archive of a post made to our 'vox-tech mailing list' by one of its subscribers.

Report this post as spam:

(Enter your email address)
Re: [vox-tech] Perl: Regex if then else
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [vox-tech] Perl: Regex if then else



Unfortunately, I don't understand the error, or how to solve it

[jdedev]/home/jstrauss/bin> cat ./tmp
#!/usr/bin/perl
@s = ('initial 256','initial 512','initial 1024','initial 2048');

foreach (@s) {
        s/(?<=initial\s+)(\d+)/$1 == 256 ? "4092" : "1024" /e;
        print "$_\n";
}

[jdedev]/home/jstrauss/bin> ./tmp
Variable length lookbehind not implemented before HERE mark in regex
m/(?<=initial\s+)(\d+) << HERE / at ./tmp line 14.



----- Original Message -----
From: "Micah Cowan" <micah@cowanbox.com>
To: <vox-tech@franz.mother.com>
Sent: Tuesday, August 14, 2001 12:55 PM
Subject: Re: [vox-tech] Perl: Regex if then else


> On Tue, Aug 14, 2001 at 12:25:48PM -0500, Jay Strauss wrote:
> > Is there any way (in perl) to do a substitution like if you find this,
> > replace it with that, else replace it with something else?
> >
> > For example I have a bunch of lines like:
> >
> > initial 256
> > initial 512
> > initial 1024
> > initial 2048
> >
> > I want to match on /initial\s+\d+/ and replace 256 with 4092 but replace
all
> > the other numbers with 1024.  I don't know (ahead of time) what the
numbers
> > are, I just know I want to replace a specific number with X and the rest
> > with Y.
>
> You can use s/(?<=initial\s+)(\d+)/ $1 == 256 ? "4092" : "1024" /e;
>
> The (?<=foo) is a lookbehind assertion, and matches only when the
> pattern is preceded by foo; but isn't itself included in the match
> string.  The 'e' switch allows you to use Perl code to generate the
> substitution.  This is a newer feature, and not available in older
> Perl versions (such as the one I have available at the moment - thus,
> the line above is untested).
>
> Micah


_________________________________________________________
Do You Yahoo!?
Get your free @yahoo.com address at http://mail.yahoo.com


LinkedIn
LUGOD Group on LinkedIn
Sign up for LUGOD event announcements
Your email address:
facebook
LUGOD Group on Facebook
'Like' LUGOD on Facebook:

Hosting provided by:
Sunset Systems
Sunset Systems offers preconfigured Linux systems, remote system administration and custom software development.

LUGOD: Linux Users' Group of Davis
PO Box 2082, Davis, CA 95617
Contact Us

LUGOD is a 501(c)7 non-profit organization
based in Davis, California
and serving the Sacramento area.
"Linux" is a trademark of Linus Torvalds.

Sponsored in part by:
Sunset Systems
Who graciously hosts our website & mailing lists!