tulsyan has asked for the wisdom of the Perl Monks concerning the following question:

MONKS,

I am new this perl group.

I need ur help. That is, Is it possible to modify the file without using any Temporary variable 

use strict;
open (JE, "< c:\\tuls\\tuls.txt") || die "Can not open the file ";

my $ou;
while (<JE>)
{
    $_=~s/findtext/changetext/g;
    $ou.=$_;
}

close(JE);
open (JE, "> c:\\tuls\\tuls.txt") ;
print JE $ou;
close (JE);

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Replies are listed 'Best First'.
Re: Modify file without any temp variable
by gopalr (Priest) on Jul 20, 2005 at 07:15 UTC

    Hi

    use strict;
my $ou;
open(JE, "+<c:\\tuls\\tuls.txt");
while(<JE>)
{
    $_=~s/findtext/changetext/g;
    $ou.=$_;
}
seek(JE, 0, 0);
print JE $ou;
close JE

    [download]
[reply]
[d/l]
      This is bad ! If the new text is shorter than the old one, the file is not truncated, and you happen to have some extra dirt at the end of the file ! (took me quite some time to figure it out)

      P!
      Are the monkeys gone yet?
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Re: Modify file without any temp variable
by GrandFather (Saint) on Jul 20, 2005 at 07:22 UTC

    Your version works fine. The following is a little more succinct:

    use strict;
use warnings;

my $fileName = "test.txt";
open (JE, "+< $fileName") || die "Can not open the file ";

my $ou = join "", <JE>;
$ou=~s/findtext/changetext/gs;
seek JE, 0, 0;
print JE $ou;
close (JE);

    [download]
    Perl is Huffman encoded by design.
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[d/l]

      Can you tell me about the seek

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[d/l]

        seek = Sets FILEHANDLE's position

        Go thorough seek

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[d/l]
Re: Modify file without any temp variable
by rev_1318 (Chaplain) on Jul 20, 2005 at 07:48 UTC
    You can use the in-place edit option of Perl (see the -i option in perlrun):
    {
    local $^I = ''; #no backup of original!
    local @ARGV = qw(c:\\tuls\\tuls.txt);
    
    while ( <ARGV> ) {
        s/find/replace/g;
        print;
    }
}

    [download]

    Paul

[reply]
[d/l]
[select]

      I think you will find that that generates a temporary file, although not an explicit one. It is an option OP should look at though.

      Perl is Huffman encoded by design.
[reply]
Re: Modify file without any temp variable
by Llew_Llaw_Gyffes (Scribe) on Jul 20, 2005 at 20:23 UTC

    Here's another approach:

    my @orig = ($/, $\);
undef($/);
undef($\);
open (JE, $file) || die "Cannot open $file";
(my $j = <JE>) =~ s/orig/new/g;

    [download]

    At this point you can either:

    close (JE);
open (JE, "> $file);
print JE $j;
close (JE);
($/, $\) = @orig;

    [download]

    or, more efficiently:

    seek (JE, 0, 0);
print JE $j;
close (JE);
($/, $\) = @orig;

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