```{index} single: IO::Seekable ``` # IO::Seekable ```{pperl-module-badges} IO::Seekable ``` supply seek based methods for I/O objects ## SYNOPSIS ```perl 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](../core/perlfunc.md) 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](../core/perlfunc.md) 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](../core/perlfunc.md), ["I/O Operators" in perlop](../core/perlop.md), [IO::Handle](Handle.md) [IO::File](File.md) ## HISTORY Derived from FileHandle.pm by Graham Barr ## Functions ### Other Functions #### `getpos` Return an opaque marker for the handle's current position. #### `setpos` Return the handle to a position previously recorded by `getpos`.