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# IO::Seekable

Perl 5 version 10.1 documentation
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# IO::Seekable

- NAME
- SYNOPSIS
- DESCRIPTION
- SEE ALSO
- HISTORY

# 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 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` 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 <gbarr@pobox.com>

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