MirOS Manual: IO::Seekable(3p)


IO::Seekable(3p)Perl Programmers Reference Guide IO::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 pos-
         sible (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 fol-
     lowing 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 v5.8.8                2005-02-05                           1

IO::Seekable(3p)Perl Programmers Reference Guide IO::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 v5.8.8                2005-02-05                           2

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