Perl File Handling: open, read, write and close files

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Opening files

Solution 1:

Opening a file in perl

open FILE, "filename.txt" or die $!; # read


open FILEHANDLE, MODE, EXPR

The available modes are the following:

Each of the above modes can also be prefixed with the + character to allow for simultaneous reading and writing.

open FILE, ">", "filename.txt" or die $!    #write


open FILE, ">filename.txt" or die $!;   #write


Solution 2:

#!/usr/bin/perlopen(FILE, "<file.txt") or die "Couldn‘t open file file.txt, $!";while(<FILE>){   print "$_";}

Following is the table which gives possible values of different modes

Solution 3:

sysopen(FILE, "file.txt", O_RDWR|O_TRUNC );

Following is the table which gives possible values of MODE

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Reading files

read a text file line-by-line

my @lines = <FILE>;

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

while (my $line = <FILE>) { ...}

read a file only a few characters at a time

open FILE, "picture.jpg" or die $!; # read

binmode FILE;

my ($buf, $data, $n);

while (($n = read FILE, $data, 4) != 0)

{ print "$n bytes read\n"; $buf .= $data; }

close(FILE);

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Writing files

open FILE, ">file.txt" or die $!; #write


print FILE $str;

close FILE;

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Closing files

open FILE1, "file.txt" or die $!; # read

open FILE2, "picture.jpg" or die $!; # read

...

close FILE2;

close FILE1;

 #====================

REF:

http://www.perlfect.com/articles/perlfile.shtml