On Thu, 28 Jan 2016 07:41:15 -0800
Jim Gibson <j...@gibson.org> wrote:
> > On Jan 28, 2016, at 1:37 AM, Frank Larry <frankylarry2...@gmail.com> wrote:
> >
> > Hi Team,
> >
> > could you please let me? i have a file which contains "Debug", i would
> > like to replace debug to "Error", when i ran the below program the out
> > showing Error message but how to save the output with new changes. Could
> > you please tell me how to fix it?
>
> The way to do this within a larger Perl program is to open a new output file,
> copy all of the possibly-modified lines to this file. Then you can rename the
> new file to the same name as the old file, and perhaps rename the old file as
> well and keep it around as a backup.
>
> >
> > open(FILE, "<filter.txt") or die "Can’t open $!\n”;
>
> The three-argument version of open is preferred here, and let’s put the file
> name in a variable and use a lexical variable for the file handle (untested):
>
> my $filename = ‘filter.txt’;
> open( my $in, ‘<‘, $filename ) or die(“Can’t open $filename for reading: $!”);
>
> # create a new file
> my $newfile = $filename . ‘.new’;
> open( my $out, ‘>’, $newfile ) or die(“Can’t create $newfile: $!”);
>
> >
> > while($line = <FILE>){
>
> while( $line = <$in> ) {
>
In addition to all that:
1. Add "use strict;" and "use warnings;" at the beginning.
2. «while ($line = <$in>)» should be «while (my $line = <$in>)»
For more information see:
http://perl-begin.org/tutorials/bad-elements/
> >
> > print "Before substituting: ", $line ,"\n";
> > $line =~ s/Debug/Error/g;
> > print "After substituting : ", $line , "\n”;
>
> print $out $line;
This is easy to confuse with:
print $out, $line;
As a result it is preferable to do:
print {$out} $line;
Or in new versions enough of perl :
$out->print($line);
Finally, there's also http://perldoc.perl.org/autodie.html .
Regards,
Shlomi Fish
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