Manpages - IO_Seekable.3perl
Table of Contents
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 numbers0
1
or2
in your code. Returns1
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, orundef
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>