


IO::Seekable(3p) Perl Programmers Reference GuideIO::Seekable(3p)


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 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.



2001-05-24                 perl v5.6.1                          1





IO::Seekable(3p) Perl Programmers Reference GuideIO::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 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>




































2001-05-24                 perl v5.6.1                          2


