IO::Seekable(3) Perl Programmers Reference Guide IO::Seekable(3)NAMEIO::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 avail
able in your C library it is used to implements get
pos, else perl emulates getpos using C's ftell() func
tion.
$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 the perlfunc manpage for complete descriptions of each
of the following supported "IO::Seekable" methods, which
are just front ends for the corresponding built-in func
tions:
$io->setpos ( 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=1 (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 con
fuse most perl IO operators except sysread and
syswrite (see the perlfunc manpage 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
the perlfunc manpage, the I/O Operators entry in the per
lop manpage, the IO::Handle manpage the IO::File manpage
HISTORY
Derived from FileHandle.pm by Graham Barr
<gbarr@pobox.com>
2001-03-18 perl v5.6.1 IO::Seekable(3)
