IO::Seekable(3pm) Perl Programmers Reference Guide 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(1), "I/O Operators" in perlop(1), IO::Handle(3), IO::File(3)
HISTORY
Derived from FileHandle.pm by Graham Barr <gbarr@pobox.com>
perl v5.38.2 2023-11-28 IO::Seekable(3pm)
perl 5.38.2 - Generated Sat Dec 7 10:14:11 CST 2024