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IO::Handle(3)							 IO::Handle(3)

NAME    [Toc]    [Back]

     IO::Handle	- supply object	methods	for I/O	handles

SYNOPSIS    [Toc]    [Back]

	 use IO::Handle;

	 $fh = new IO::Handle;
	 if ($fh->fdopen(fileno(STDIN),"r")) {
	     print $fh->getline;

	 $fh = new IO::Handle;
	 if ($fh->fdopen(fileno(STDOUT),"w")) {
	     $fh->print("Some text\n");

	 use IO::Handle	'_IOLBF';
	 $fh->setvbuf($buffer_var, _IOLBF, 1024);

	 undef $fh;	  # automatically closes the file if it's open

	 autoflush STDOUT 1;

DESCRIPTION    [Toc]    [Back]

     IO::Handle	is the base class for all other	IO handle classes. It is not
     intended that objects of IO::Handle would be created directly, but
     instead IO::Handle	is inherited from by several other classes in the IO

     If	you are	reading	this documentation, looking for	a replacement for the
     FileHandle	package, then I	suggest	you read the documentation for

     A IO::Handle object is a reference	to a symbol (see the Symbol package)

CONSTRUCTOR    [Toc]    [Back]

     new ()
	 Creates a new IO::Handle object.

     new_from_fd ( FD, MODE )
	 Creates a IO::Handle like new does.  It requires two parameters,
	 which are passed to the method	fdopen;	if the fdopen fails, the
	 object	is destroyed. Otherwise, it is returned	to the caller.

METHODS    [Toc]    [Back]

     See the perlfunc manpage for complete descriptions	of each	of the
     following supported IO::Handle methods, which are just front ends for the
     corresponding built-in functions:

									Page 1

IO::Handle(3)							 IO::Handle(3)


     See the perlvar manpage for complete descriptions of each of the
     following supported IO::Handle methods:


     Furthermore, for doing normal I/O you might need these:

     $fh->fdopen ( FD, MODE )
	  fdopen is like an ordinary open except that its first	parameter is
	  not a	filename but rather a file handle name,	a IO::Handle object,
	  or a file descriptor number.

	  Returns true if the object is	currently a valid file descriptor.

	  This works like <$fh>	described in the section on I/O	Operators in
	  the perlop manpage except that it's more readable and	can be safely
	  called in an array context but still returns just one	line.

	  This works like <$fh>	when called in an array	context	to read	all
	  the remaining	lines in a file, except	that it's more readable.  It
	  will also croak() if accidentally called in a	scalar context.

     $fh->ungetc ( ORD )
	  Pushes a character with the given ordinal value back onto the	given
	  handle's input stream.

									Page 2

IO::Handle(3)							 IO::Handle(3)

     $fh->write	( BUF, LEN [, OFFSET }\] )
	  This write is	like write found in C, that is it is the opposite of
	  read.	The wrapper for	the perl write function	is called

	  Flush	the given handle's buffer.

	  Returns a true value if the given handle has experienced any errors
	  since	it was opened or since the last	call to	clearerr.

	  Clear	the given handle's error indicator.

     If	the C functions	setbuf() and/or	setvbuf() are available, then
     IO::Handle::setbuf	and IO::Handle::setvbuf	set the	buffering policy for
     an	IO::Handle.  The calling sequences for the Perl	functions are the same
     as	their C	counterparts--including	the constants _IOFBF, _IOLBF, and
     _IONBF for	setvbuf()--except that the buffer parameter specifies a	scalar
     variable to use as	a buffer.  WARNING: A variable used as a buffer	by
     setbuf or setvbuf must not	be modified in any way until the IO::Handle is
     closed or setbuf or setvbuf is called again, or memory corruption may
     result!  Note that	you need to import the constants _IOFBF, _IOLBF, and
     _IONBF explicitly.

     Lastly, there is a	special	method for working under -T and	setuid/gid

	  Marks	the object as taint-clean, and as such data read from it will
	  also be considered taint-clean. Note that this is a very trusting
	  action to take, and appropriate consideration	for the	data source
	  and potential	vulnerability should be	kept in	mind.

NOTE    [Toc]    [Back]

     A IO::Handle object is a GLOB reference. Some modules that	inherit	from
     IO::Handle	may want to keep object	related	variables in the hash table
     part of the GLOB. In an attempt to	prevent	modules	trampling on each
     other I propose the that any such module should prefix its	variables with
     its own name separated by _'s. For	example	the IO::Socket module keeps a
     timeout variable in 'io_socket_timeout'.

SEE ALSO    [Toc]    [Back]

     the perlfunc manpage, the section on I/O Operators	in the perlop manpage,
     the IO::File manpage

BUGS    [Toc]    [Back]

     Due to backwards compatibility, all filehandles resemble objects of class
     IO::Handle, or actually classes derived from that class.  They actually
     aren't.  Which means you can't derive your	own class from IO::Handle and
     inherit those methods.

									Page 3

IO::Handle(3)							 IO::Handle(3)

HISTORY    [Toc]    [Back]

     Derived from FileHandle.pm	by Graham Barr <bodg@tiuk.ti.com>

									PPPPaaaaggggeeee 4444
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