Skip site navigation (1)Skip section navigation (2)

FreeBSD Manual Pages

  
 
  

home | help
FileHandle(3)	       Perl Programmers	Reference Guide		 FileHandle(3)

NAME
       FileHandle - supply object methods for filehandles

SYNOPSIS
	   use FileHandle;

	   $fh = FileHandle->new;
	   if ($fh->open("< file")) {
	       print <$fh>;
	       $fh->close;
	   }

	   $fh = FileHandle->new("> FOO");
	   if (defined $fh) {
	       print $fh "bar\n";
	       $fh->close;
	   }

	   $fh = FileHandle->new("file", "r");
	   if (defined $fh) {
	       print <$fh>;
	       undef $fh;	# automatically	closes the file
	   }

	   $fh = FileHandle->new("file", O_WRONLY|O_APPEND);
	   if (defined $fh) {
	       print $fh "corge\n";
	       undef $fh;	# automatically	closes the file
	   }

	   $pos	= $fh->getpos;
	   $fh->setpos($pos);

	   $fh->setvbuf($buffer_var, _IOLBF, 1024);

	   ($readfh, $writefh) = FileHandle::pipe;

	   autoflush STDOUT 1;

DESCRIPTION
       NOTE: This class	is now a front-end to the IO::*	classes.

       "FileHandle::new" creates a "FileHandle", which is a reference to a
       newly created symbol (see the "Symbol" package).	 If it receives	any
       parameters, they	are passed to "FileHandle::open"; if the open fails,
       the "FileHandle"	object is destroyed.  Otherwise, it is returned	to the
       caller.

       "FileHandle::new_from_fd" creates a "FileHandle"	like "new" does.  It
       requires	two parameters,	which are passed to "FileHandle::fdopen"; if
       the fdopen fails, the "FileHandle" object is destroyed.	Otherwise, it
       is returned to the caller.

       "FileHandle::open" accepts one parameter	or two.	 With one parameter,
       it is just a front end for the built-in "open" function.	 With two
       parameters, the first parameter is a filename that may include
       whitespace or other special characters, and the second parameter	is the
       open mode, optionally followed by a file	permission value.

       If "FileHandle::open" receives a	Perl mode string (">", "+<", etc.)  or
       a POSIX fopen() mode string ("w", "r+", etc.), it uses the basic	Perl
       "open" operator.

       If "FileHandle::open" is	given a	numeric	mode, it passes	that mode and
       the optional permissions	value to the Perl "sysopen" operator.  For
       convenience, "FileHandle::import" tries to import the O_XXX constants
       from the	Fcntl module.  If dynamic loading is not available, this may
       fail, but the rest of FileHandle	will still work.

       "FileHandle::fdopen" is like "open" except that its first parameter is
       not a filename but rather a file	handle name, a FileHandle object, or a
       file descriptor number.

       If the C	functions fgetpos() and	fsetpos() are available, then
       "FileHandle::getpos" returns an opaque value that represents the
       current position	of the FileHandle, and "FileHandle::setpos" uses that
       value to	return to a previously visited position.

       If the C	function setvbuf() is available, then "FileHandle::setvbuf"
       sets the	buffering policy for the FileHandle.  The calling sequence for
       the Perl	function is the	same as	its C counterpart, including the
       macros "_IOFBF",	"_IOLBF", and "_IONBF",	except that the	buffer
       parameter specifies a scalar variable to	use as a buffer.  WARNING: A
       variable	used as	a buffer by "FileHandle::setvbuf" must not be modified
       in any way until	the FileHandle is closed or until
       "FileHandle::setvbuf" is	called again, or memory	corruption may result!

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

	   close
	   fileno
	   getc
	   gets
	   eof
	   clearerr
	   seek
	   tell

       See perlvar for complete	descriptions of	each of	the following
       supported "FileHandle" methods:

	   autoflush
	   output_field_separator
	   output_record_separator
	   input_record_separator
	   input_line_number
	   format_page_number
	   format_lines_per_page
	   format_lines_left
	   format_name
	   format_top_name
	   format_line_break_characters
	   format_formfeed

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

       $fh->print
	   See "print" in perlfunc.

       $fh->printf
	   See "printf"	in perlfunc.

       $fh->getline
	   This	works like <$fh> described in "I/O Operators" in perlop	except
	   that	it's more readable and can be safely called in a list context
	   but still returns just one line.

       $fh->getlines
	   This	works like <$fh> when called in	a list 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.

       There are many other functions available	since FileHandle is descended
       from IO::File, IO::Seekable, and	IO::Handle.  Please see	those
       respective pages	for documentation on more functions.

SEE ALSO
       The IO extension, perlfunc, "I/O	Operators" in perlop.

perl v5.26.0			  2017-04-19			 FileHandle(3)

NAME | SYNOPSIS | DESCRIPTION | SEE ALSO

Want to link to this manual page? Use this URL:
<https://www.freebsd.org/cgi/man.cgi?query=FileHandle&sektion=3&manpath=FreeBSD+12.0-RELEASE+and+Ports>

home | help