IO::Seekable

IO::Seekable(3)        Perl Programmers Reference Guide        IO::Seekable(3)



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 meth-
       ods 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() func-
           tion is available in your C library it is used to implements get-
           pos, 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 fail-
           ure.

       See perlfunc for complete descriptions of each of the following sup-
       ported "IO::Seekable" methods, which are just front ends for the corre-
       sponding 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 opera-
           tors 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>



perl v5.8.6                       2001-09-21                   IO::Seekable(3)