Re: Reading from standard input

Thanks John ! I finally understood the concept of '-' stream.

Harpreet

John W. Krahn wrote:
Harpreet wrote:

I am learning perl scripting and was reading an online tutorial where i
encountered this code(at the end of message). The first part of the
code (reading from file) has been pasted as-is and the second(reading
from standard input stream) was written by me. When I execute the
program, I get the correct result from the first one and then I type
into the stream some data but I don't know how to end it. I used the
conventional unix "dot-enter" scheme but it didn't work. Neither did
Ctrl-D. I found some examples which read from <STDIN> and worked with a
while loop. Can somebody explain me why reading from the standard input
doesn't work the way I have written ?

Because you are not reading from the standard input.

If I am missing the escape
character to denote the end of stream, please mention it.

Any pointers will be appreciated.


<CODE>
#!usr/local/bin/perl

You are using a relative path when you should be using an absolute path:

#!/usr/local/bin/perl

And don't forget:

use warnings;
use strict;


$file = '/etc/passwd'; # Name the file
open(INFO, $file); # Open the file

You should *ALWAYS* verify that the file opened correctly:

open(INFO, $file) or die "Cannot open '$file' $!";

@lines = <INFO>; # Read it into an array
close(INFO); # Close the file
print @lines; # Print the array

open(INFO, '-');

You should *ALWAYS* verify that the file opened correctly:

open(INFO, '-') or die "Cannot open '-' $!";

You are trying to open the file '-', standard input is not involved when
opening a plain file.

The *only* time that '-' has anything to do with standard input is when @ARGV
and <> are used:

local @ARGV = '-';

while ( <> ) { # read from STDIN because @ARGV contains '-'
print;
}

@lines2 = <INFO>; # Read it into an array
close(INFO);
print @lines2;
</CODE>



John
--
use Perl;
program
fulfillment

.

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