Perl file read/write

Perl file handling: open, read, write and close files #======================== 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:

Mode	Operand	Create	Truncate
Read	<
Write	>	?	?
Append	>	?

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

Mode	Operand	Create	Truncate
Read/write	+ <
Read/write	+>	?	?
Read/append	+>	?

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

Entities	Definition
<Or R	Read Only access
> Or W	Creates, writes, and truncates
> Or	Writes, appends, and creates
+ <Or R +	Reads and writes
+> Or W +	Reads, writes, creates, and truncates
+ >> Or a +	Reads, writes, appends, and creates

Solution 3:

 

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

Following is the table which gives possible values of Mode

Entities	Definition
O_rdwr	Read and Write
O_rdonly	Read Only
O_wronly	Write only
O_creat	Create the file
O_append	Append the file
O_trunc	Truncate the file
O_excl	Stops if file already exists
O_nonblock	Non-blocking usability

 

#=============================== 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);

#================================

Writing files

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


print FILE $str;

close FILE;

#=============================== 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