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>