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IO::Seekable

Section: Perl Programmers Reference Guide (3)
Updated: 2001-09-21
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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>


 

Index

NAME
SYNOPSIS
DESCRIPTION
SEE ALSO
HISTORY




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