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Top Forums Shell Programming and Scripting Perl : How is file handling working here?? Post 302831873 by siddharthjindal on Friday 12th of July 2013 05:56:38 AM
Old 07-12-2013
Perl : How is file handling working here??

Hi,

I have a perl script which is just reading from the file but what I would like to understand is how the counter is moving without using the loop in the script.

Below are the details:
Code:
$ more /tmp/abc.txt
This is 0
This is 1
This is 2
This is 3
This is 4
This is 5
This is 6
This is 7
This is 8
This is 9

Script to read the above file is as :
Code:
$ more file1.pl
#!/usr/bin/perl
#
sub readfile
{
     my ($rec,$INFO);
     $INF=shift;
     if (defined($rec = scalar <$INF>))
     {
          print $rec;
     }
}
$file='/tmp/abc.txt';
open(xyz,$file);
$i=0;
$tes=readfile(xyz);
$tes=readfile(xyz);

when I am executing the above script, it is throwing the output as :

Code:
$ perl file1.pl
This is 0
This is 1

How counter in the file is moving to next row when I am not moving it and I am also not using any loops anywhere? I would just like to understand that? Does that mean loops are not required for moving through the file or I am getting it wrong somewhere?

Thanks in advance for any help on this!


Moderator's Comments:
Mod Comment Use code tags please, see PM.

Last edited by zaxxon; 07-12-2013 at 07:51 AM.. Reason: code tags and indention
 

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service(8)						      System Manager's Manual							service(8)

NAME
service - run a System V init script SYNOPSIS
service SCRIPT COMMAND [OPTIONS] service --status-all service --help | -h | --version DESCRIPTION
service runs a System V init script in as predictable environment as possible, removing most environment variables and with current working directory set to /. The SCRIPT parameter specifies a System V init script, located in /etc/init.d/SCRIPT. The supported values of COMMAND depend on the invoked script, service passes COMMAND and OPTIONS it to the init script unmodified. All scripts should support at least the start and stop commands. As a special case, if COMMAND is --full-restart, the script is run twice, first with the stop command, then with the start command. service --status-all runs all init scripts, in alphabetical order, with the status command. EXIT CODES
service calls the init script and returns the status returned by it. FILES
/etc/init.d The directory containing System V init scripts. ENVIRONMENT
LANG, TERM The only environment variables passed to the init scripts. SEE ALSO
/etc/init.d/skeleton, update-rc.d(8), init(8), invoke-rc.d(8). Jan 2006 service(8)
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