Entities	Definition
< or r	Read Only Access
> or w	Creates, Writes, and Truncates
>> or a	Writes, Appends, and Creates
+< or r+	Reads and Writes
+> or w+	Reads, Writes, Creates, and Truncates
+>> or a+	Reads, Writes, Appends, and Creates

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

Operator	Definition
-A	Script start time minus file last access time, in days.
-B	Is it a binary file?
-C	Script start time minus file last inode change time, in days.
-M	Script start time minus file modification time, in days.
-O	Is the file owned by the real user ID?
-R	Is the file readable by the real user ID or real group?
-S	Is the file a socket?
-T	Is it a text file?
-W	Is the file writable by the real user ID or real group?
-X	Is the file executable by the real user ID or real group?
-b	Is it a block special file?
-c	Is it a character special file?
-d	Is the file a directory?
-e	Does the file exist?
-f	Is it a plain file?
-g	Does the file have the setgid bit set?
-k	Does the file have the sticky bit set?
-l	Is the file a symbolic link?
-o	Is the file owned by the effective user ID?
-p	Is the file a named pipe?
-r	Is the file readable by the effective user or group ID?
-s	Returns the size of the file, zero size = empty file.
-t	Is the filehandle opened by a TTY (terminal)?
-u	Does the file have the setuid bit set?
-w	Is the file writable by the effective user or group ID?
-x	Is the file executable by the effective user or group ID?
-z	Is the file size zero?

open FILEHANDLE, EXPR
open FILEHANDLE

sysopen FILEHANDLE, FILENAME, MODE, PERMS
sysopen FILEHANDLE, FILENAME, MODE

						
Open Function

open(DATA, "<file.txt");

						

#!/usr/bin/perl

open(DATA, "<file.txt") or die "Couldn't open file file.txt, $!";

while(<DATA>){
   print "$_";
}

						

open(DATA, ">file.txt") or die "Couldn't open file file.txt, $!";

						

open(DATA, "+<file.txt"); or die "Couldn't open file file.txt, $!";

						

open DATA, "+>file.txt" or die "Couldn't open file file.txt, $!";

						

open(DATA,">>file.txt") || die "Couldn't open file file.txt, $!";

						

open(DATA,"+>>file.txt") || die "Couldn't open file file.txt, $!";

						
Sysopen Function

sysopen(DATA, "file.txt", O_RDWR);

						

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

						
Close Function

close FILEHANDLE
close

						

close(DATA) || die "Couldn't close file properly";

						
The <FILEHANDL> Operator

#!/usr/bin/perl

print "What is your name?\n";
$name = <STDIN>;
print "Hello $name\n";

						

#!/usr/bin/perl

open(DATA,"<import.txt") or die "Can't open data";
@lines = <DATA>;
close(DATA);

						
getc Function

getc FILEHANDLE
getc

						
read Function

read FILEHANDLE, SCALAR, LENGTH, OFFSET
read FILEHANDLE, SCALAR, LENGTH

						
print Function

print FILEHANDLE LIST
print LIST
print

						

print "Hello World!\n";

						
Copying Files

#!/usr/bin/perl

# Open file to read
open(DATA1, "<file1.txt");

# Open new file to write
open(DATA2, ">file2.txt");

# Copy data from one file to another.
while(<DATA1>)
{
   print DATA2 $_;
}
close( DATA1 );
close( DATA2 );

						
Renaming a file

#!/usr/bin/perl

rename ("/usr/test/file1.txt", "/usr/test/file2.txt" );


						
Deleting an exiting file

#!/usr/bin/perl

unlink ("/usr/test/file1.txt");


						
Positioning inside a file

tell FILEHANDLE
tell

						

seek FILEHANDLE, POSITION, WHENCE

						

seek DATA, 256, 0;

						
File Information

#/usr/bin/perl

my $file = "/usr/test/file1.txt";
my (@description, $size);
if (-e $file)
{
   push @description, 'binary' if (-B _);
   push @description, 'a socket' if (-S _);
   push @description, 'a text file' if (-T _);
   push @description, 'a block special file' if (-b _);
   push @description, 'a character special file' if (-c _);
   push @description, 'a directory' if (-d _);
   push @description, 'executable' if (-x _);
   push @description, (($size = -s _)) ? "$size bytes" : 'empty';
   print "$file is ", join(', ',@description),"\n";
}