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 provides 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() function is available in your C library it is used to imple-
           ments getpos, 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 supported "IO::Seekable"
       methods, which are just front ends for the corresponding 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 operators 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 <>



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