# phpman > man > IO::Seekable

## NAME
    [IO::Seekable](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3ASeekable/markdown) - supply seek based methods for I/O objects

## SYNOPSIS
        use [IO::Seekable](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3ASeekable/markdown);
        package [IO::Something](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3ASomething/markdown);
        @ISA = qw([IO::Seekable](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3ASeekable/markdown));

## DESCRIPTION
    "[IO::Seekable](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3ASeekable/markdown)" does not have a constructor of its own as it is intended to be inherited by other
    "[IO::Handle](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3AHandle/markdown)" 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](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3AFile/markdown), 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 implements 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](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3ASeekable/markdown)"
    methods, which are just front ends for the corresponding built-in functions:

    $io->seek ( POS, WHENCE )
        Seek the [IO::File](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3AFile/markdown) 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](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3AFile/markdown)'s position using the system call [lseek(2)](https://www.chedong.com/phpMan.php/man/lseek/2/markdown)
        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](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3AFile/markdown)'s current position, or -1 on error.

## SEE ALSO
    perlfunc, "I/O Operators" in perlop, [IO::Handle](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3AHandle/markdown) [IO::File](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3AFile/markdown)

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