CODEWITHSUNDEEP
perlfile
kay
kay

Reputation: 186

Read file from STDIN and write to STDOUT

I want to read html files entered from STDIN perform some function and then write another html file to STDOUT. My problem is I have to give file in the stated manner. I have tried many things but nothing is working good. Nothing is getting printed

my command line prompt

perl universe.pl<sun.html>galaxy.html

my code -

open(my $in, "<&STDIN")     or die "Can't dup STDIN: $!";
open(my $out, ">&STDOUT")     or die "Can't dup STDOUT: $!";

my @lines = <$in>;
foreach(@lines) {
   push(@newlines,$_);
   say "Lines pushing:", $_;
}

Upvotes: 0

Views: 3368

Answers (4)

james
james

Reputation: 1

Below is my own effort:

#!/bin/perl
while (<>)
    {
        print $_;
    }

I like to start from the simplest possible example before I undertake more complex tasks.

Being barely an intermediate-level perl programmer, I am not sure how critical these statements are and what they are for:

use strict; use warnings;

... so I temporarily omitted them from the start of my script and it still worked.

Upvotes: -2

James Raynard
James Raynard

Reputation: 19

I had this problem with a script which was run from inside another Perl script.

The solution was to set $| in the second script (the one which executes the script which reads from STDIN).

Upvotes: -1

Jonathan Leffler
Jonathan Leffler

Reputation: 754900

You don't need to open STDIN or STDOUT; they're always ready opened.

You don't need to slurp the whole file into memory as you do with:

my @lines = <$in>;

You never use $out which should be indicative of a problem.

while (<>)
{
    print mapping_func($_);
}

where mapping_func() is your function that does the relevant transform on its input string and returns the mapped result:

sub mapping_func
{
    my($string) = @_;
    $string =~ s/html/HTML/gi;
    return $string;
}

Upvotes: 2

Gilles Qu&#233;not
Gilles Qu&#233;not

Reputation: 185700

Using the magic diamond operator <>, you will able to do what you asked. But please to provide some more search efforts next time.

use strict; use warnings;

while (my $line = <>) {
   # do something with $line
}

Last but not least; if you have to parse HTML the good way, have a look to HTML::TreeBuilder::XPath or just HTML::TreeBuilder

Upvotes: 1

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