


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
           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.





perl v5.10.1                2006-03-28                          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
           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>





































perl v5.10.1                2006-03-28                          2


