Perl Script help please

ck346 has asked for the wisdom of the Perl Monks concerning the following question:

I'm new to perl and have this small perl script I made and I need to change it from displaying the result on the terminal window to outputting it to a file for example like demo.txt instead. I have spent all day and can't figure it out. Any help would be greatly appreciated.

#!/usr/bin/perl -w

print "Content-type: text/html\n\n";

foreach my $key (sort keys %ENV) {
print "\$ENV{$key} = $ENV{$key}<br/>\n";
}

exit;
[download]

Comment on Perl Script help please Download Code

Replies are listed 'Best First'.

Re: Perl Script help please
by Athanasius (Archbishop) on Oct 05, 2015 at 03:08 UTC

Hello ck346, and welcome to the Monastery!

First,

See How do I compose an effective node title?
Please put code inside <code> ... </code> tags; see Markup in the Monastery.
Always use strict; as well as warnings.
Please review How do I post a question effectively? In particular, instead of saying I have spent all day and can't figure it out, show what you’ve tried and how it failed.

Now to the question of printing to a file. Do this in three stages:

Open the file for writing. Use the 3-argument form of open together with a lexical (my) filehandle, and check for errors:

my $output_file = 'demo.txt';

open(my $out_fh, '>', $output_file)
    or die "Cannot open file '$output_file' for writing: $!";
[download]

Print to the filehandle as you would to the console: just put the filehandle as the first argument to open, with no comma between the filehandle and the next argument:
```
print $out_fh "\$ENV{$key} = $ENV{$key}\n";
[download]
```

Close the filehandle when you’re finished writing to the output file:

close $out_fh
    or die "Cannot close file '$output_file': $!";
[download]

See perlopentut.

Hope that helps,

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

[reply]
[d/l]
[select]

Re: Perl Script help please
by davido (Cardinal) on Oct 05, 2015 at 03:14 UTC

You can use shell redirection if you like.

./myscript.pl > demo.txt
[download]

Or you could modify the script itself:

#!/usr/bin/perl

use strict;
use warnings;

open my $fh, '>', 'demo.txt' or die $!;

print $fh "Content-type: text/html\n\n";

foreach my $key (sort keys %ENV) {
    print $fh "\$ENV{$key} = $ENV{$key}<br />\n";
}

close $fh or die $!;
[download]

I suggest you spend 30 minutes reading perlintro. If this is homework, you're going to need to actually learn this, and perlintro is a good start.

Dave

[reply]
[d/l]
[select]