Perl write and read on same file Post: 302845615

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Top Forums Shell Programming and Scripting Perl write and read on same file Post 302845615 by royalibrahim on Thursday 22nd of August 2013 02:43:45 AM

08-22-2013

Registered User

Perl write and read on same file

Hi,

I am trying to do a write operation followed by a read operation on the same file through Perl, expecting the output produced by read to contain the new lines added, as follows:

Code:

#! /usr/bin/perl -w

open FH, "+< testfile" or die "$@";
print FH  "New content added\n";
while (my $line = <FH>) {
    print "$line";
}
close(FH);

but the above code is sometimes corrupting the file's data (like replacing, globbering spaces etc.,). I have tried to flush the buffer but to no avail:

Code:

open FH, "+>> testfile" or die "$@";
$| = 1;
print FH  "New content added\n";
while (my $line = <FH>) {
    print "$line";
}
FH->autoflush(1);
close(FH);

I have even changed the mode to '+>', '+>>', but nothing works (i.e) the output is not printed with the lines recently added unless I close the file handle and reopen the file for reading.

Kindly help me how to modify the above Perl code to see the contents that are added by the previous write operation without closing the handle. Thank you.

royalibrahim

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LEARN ABOUT DEBIAN

config::model::backend::debian::dpkg::patch

Config::Model::Backend::Debian::Dpkg::Patch(3pm)	User Contributed Perl Documentation	  Config::Model::Backend::Debian::Dpkg::Patch(3pm)

NAME

       Config::Model::Backend::Debian::Dpkg::Patch - Read and write Debian Dpkg Patch information

VERSION

       version 2.021

SYNOPSIS

       No synopsis. This class is dedicated to configuration class "Debian::Dpkg::Patch"

DESCRIPTION

       This module is used directly by Config::Model to read or write the content of Debian "Patch" file.

       All "Patch" files keyword are read in a case-insensitive manner.

CONSTRUCTOR

   new ( node => $node_obj, name => 'Debian::Dpkg::Patch' ) ;
       Inherited from Config::Model::Backend::Any. The constructor will be called by Config::Model::AutoRead.

   read ( io_handle => ... )
       Of all parameters passed to this read call-back, only "io_handle" is used. This parameter must be IO::File object already opened for read.

       It can also be undef. In this case, "read()" will return 0.

       When a file is read,  "read()" will return 1.

   write ( io_handle => ... )
       Of all parameters passed to this write call-back, only "io_handle" is used. This parameter must be IO::File object already opened for
       write.

       "write()" will return 1.

AUTHOR

       Dominique Dumont, (ddumont at cpan dot org)

SEE ALSO

       Config::Model, Config::Model::AutoRead, Config::Model::Backend::Any,

perl v5.14.2							    2012-11-09			  Config::Model::Backend::Debian::Dpkg::Patch(3pm)