IO::Seekable(3p)Perl Programmers Reference Guide IO::Seekable(3p)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 pos-
sible (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 fol-
lowing 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.
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IO::Seekable(3p)Perl Programmers Reference Guide IO::Seekable(3p)
$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>
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