IO::Seekable

IO::Seekable(3)	       Perl Programmers Reference Guide	      IO::Seekable(3)



NAME
       IO::Seekable - supply seek based methods for I/O objects

SYNOPSIS
	   use IO::Seekable;
	   package IO::Something;
	   @ISA = qw(IO::Seekable);

DESCRIPTION
       "IO::Seekable" does not have a constructor of its own as it is
       intended to be inherited by other "IO::Handle" based objects. It pro-
       vides methods which allow seeking of the file descriptors.

       $io->getpos
	   Returns an opaque value that represents the current position of
	   the IO::File, or "undef" if this is not possible (eg an unseekable
	   stream such as a terminal, pipe or socket). If the fgetpos() func-
	   tion is available in your C library it is used to implements get-
	   pos, else perl emulates getpos using C’s ftell() function.

       $io->setpos
	   Uses the value of a previous getpos call to return to a previously
	   visited position. Returns "0 but true" on success, "undef" on
	   failure.

       See perlfunc for complete descriptions of each of the following sup-
       ported "IO::Seekable" methods, which are just front ends for the cor-
       responding built-in functions:

       $io->seek ( POS, WHENCE )
	   Seek the IO::File to position POS, relative to WHENCE:

	   WHENCE=0 (SEEK_SET)
		   POS is absolute position. (Seek relative to the start of
		   the file)

	   WHENCE=1 (SEEK_CUR)
		   POS is an offset from the current position. (Seek relative
		   to current)

	   WHENCE=2 (SEEK_END)
		   POS is an offset from the end of the file. (Seek relative
		   to end)

	   The SEEK_* constants can be imported from the "Fcntl" module if
	   you don’t wish to use the numbers 0 1 or 2 in your code.

	   Returns 1 upon success, 0 otherwise.

       $io->sysseek( POS, WHENCE )
	   Similar to $io->seek, but sets the IO::File’s position using the
	   system call lseek(2) directly, so will confuse most perl IO opera-
	   tors except sysread and syswrite (see perlfunc for full details)

	   Returns the new position, or "undef" on failure.  A position of
	   zero is returned as the string "0 but true"

       $io->tell
	   Returns the IO::File’s current position, or -1 on error.

SEE ALSO
       perlfunc, "I/O Operators" in perlop, IO::Handle IO::File

HISTORY
       Derived from FileHandle.pm by Graham Barr <gbarr@pobox.com>



perl v5.8.8			  2001-09-21		      IO::Seekable(3)