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Re: Search and replace

by Athanasius (Monsignor)
on Jan 31, 2013 at 15:28 UTC ( #1016340=note: print w/ replies, xml ) Need Help??


in reply to Search and replace

Use the substitution operator s///g like this:

1:30 >perl -wE "my $found = 'ENV{\"VCINSTALLDIR\"}\ATLMFC\LIB\amd64;E +NV{\"LIBPATH\"}'; $found =~ s/ENV{\"(.*?)\"}/\$ENV(\"$1\")/g; say $fo +und;" $ENV("VCINSTALLDIR")\ATLMFC\LIB\amd64;$ENV("LIBPATH") 1:30 >

Within the substitution, the parentheses capture the “value” text which is used in the replacement as $1. The /g modifier tells the regex engine to keep searching and substituting until the string is exhausted.

See perlretut and perlre.

Hope that helps,

Athanasius <°(((><contra mundum Iustus alius egestas vitae, eros Piratica,


Comment on Re: Search and replace
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Re^2: Search and replace
by Bharath666 (Novice) on Jan 31, 2013 at 15:53 UTC

    Thank you!! Really I am weak in handling regex of this kind. Thank you soooo much

      Also if you don't mind can you please explain me how exactly this command works

      $found =~ s/ENV{\"(.*?)\"}/\$ENV(\"$1\")/g;

      Thanks!!

        I thought I already had. :-) But OK, let’s add an /x modifier to the regex to make it easier to break apart:

        $found =~ s/ ENV{\" # match the characters: ENV{" (.*?) # followed by any characters -- this sequence +is the "value", and the parentheses capture it into the special varia +ble $1 \"} # followed by: "} / \$ENV( # and substitute a literal: $ENV(" $1 # followed by the captured "value" \") # followed by: ") /gx; # and repeat the search & replacement to the e +nd of $found

        Notes:

        • The double quotes are backslashed only because I was using a one-liner (and I’m on Windows). This is unnecessary in a .pl script. (But the $ must be backslashed to show that it is literal, not the special symbol for “match the end of a line” (in the search part) or a sigil denoting a scalar variable to be interpolated (in the replacement part). Update: Added the words from “(in the search part)” to the end of the sentence.)

        • The ? in the capture group (.*?) makes the match non-greedy. So the regex engine looks for the fewest number of characters occurring between ENV{" and "}. Without the ?, the match would be greedy, and on the string:

          ENV{"VCINSTALLDIR"}\ATLMFC\LIB\amd64;ENV{"LIBPATH"}

          it would match

          VCINSTALLDIR"}\ATLMFC\LIB\amd64;ENV{"LIBPATH
        • which is not what we want!

        Hope that helps,

        Athanasius <°(((><contra mundum Iustus alius egestas vitae, eros Piratica,

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