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




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(1), "I/O Operators" in perlop(3), IO::Handle(3), IO::File(3)


HISTORY

       Derived from FileHandle.pm by Graham Barr <gbarr@pobox.com>



perl v5.24.0                      2015-10-14                 IO::Seekable(3pm)

perl 5.24 - Generated Sun Nov 13 19:44:16 CST 2016
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