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Perl Regex substitution: replace nth occurrance
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Subject Author Date
Perl Regex substitution: replace nth occurrance Yogi 04-09-2008
Posted by Yogi on April 9, 2008, 2:44 am
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 Hi Guys,
I have a variable say:
$x = "this is test program with test inputs";

My requirement is to replace nth occurrance of "test" with something
else. how to achieve the same using perl regex. if i do something
like:
$x =~ s/test/java/g;

This is going to replace all occurrance of test with "java" but my
requirement is to replace say 2nd occurrance only. Any help?

Regards.

Posted by Frank Seitz on April 9, 2008, 3:05 am
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 Yogi wrote:
> I have a variable say:
> $x = "this is test program with test inputs";
>
> My requirement is to replace nth occurrance of "test" with something
> else. how to achieve the same using perl regex. if i do something
> like:
> $x =~ s/test/java/g;
>
> This is going to replace all occurrance of test with "java" but my
> requirement is to replace say 2nd occurrance only. Any help?

perldoc -q nth

Frank
--
Dipl.-Inform. Frank Seitz; http://www.fseitz.de/
Anwendungen für Ihr Internet und Intranet
Tel: 04103/180301; Fax: -02; Industriestr. 31, 22880 Wedel

Posted by Yogi on April 9, 2008, 4:12 am
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> Yogi wrote:
> > I have a variable say:
> > $x =3D "this is test program with test inputs";
>
> > My requirement is to replace nth occurrance of "test" with something
> > else. how to achieve the same using perl regex. if i do something
> > like:
> > $x =3D~ s/test/java/g;
>
> > This is going to replace all occurrance of test with "java" but my
> > requirement is to replace say 2nd occurrance only. Any help?
>
> perldoc -q nth
>
> Frank
> --
> Dipl.-Inform. Frank Seitz;http://www.fseitz.de/
> Anwendungen f=FCr Ihr Internet und Intranet
> Tel: 04103/180301; Fax: -02; Industriestr. 31, 22880 Wedel

Thanks Frank for your help. :)
Regards,
-Yogi

Posted by John W. Krahn on April 9, 2008, 2:08 pm
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Yogi wrote:
> Hi Guys,
> I have a variable say:
> $x = "this is test program with test inputs";
>
> My requirement is to replace nth occurrance of "test" with something
> else. how to achieve the same using perl regex. if i do something
> like:
> $x =~ s/test/java/g;
>
> This is going to replace all occurrance of test with "java" but my
> requirement is to replace say 2nd occurrance only. Any help?

$ perl -le'
my $test = q[ 1 test 2 test 3 test 4 test 5 test 6 test 7 test ];
print $test;
my $count;
my $to_java = 4;
while ( $test =~ /test/g ) {
if ( $to_java == ++$count ) {
substr $test, $-[0], $+[0] - $-[0], q[java];
}
}
print $test;
'
1 test 2 test 3 test 4 test 5 test 6 test 7 test
1 test 2 test 3 test 4 java 5 test 6 test 7 test



John
--
Perl isn't a toolbox, but a small machine shop where you
can special-order certain sorts of tools at low cost and
in short order. -- Larry Wall

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