io::seekable(3pm)
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>