NAME

IO::Pipe::Producer - Perl extension for IO::Pipe

SYNOPSIS

  #Example 1 (Call a subroutine & grab its standard output):
 
  use IO::Pipe::Producer;
  $obj = new IO::Pipe::Producer();
  $stdout_file_handle =
    $obj->getSubroutineProducer(\&mysub,
                                @mysub_params);
  while(<$stdout_file_handle>)
    {print}
  close($stdout_file_handle);
 
  #Example 2 (Call a subroutine & grab its standard output & standard error):
 
  ($stdout_file_handle,$stderr_file_handle) =
    $obj->getSubroutineProducer(\&mysub,
                                @mysub_params);
 
  #It is recommended to use IO::Select when reading more than 1 file handle:
  use IO::Select;
  my $sel = new IO::Select;
  $sel->add($stdout_file_handle,$stderr_file_handle);
  while(my @fhs = $sel->can_read())
    {
      foreach my $fh (@fhs)
        {
          my $line = <$fh>;
          unless(defined($line))
            {
              $sel->remove($fh);
              close($fh);
              next;
            }
          if($fh == $stdout_file_handle)
            {$messages .= $line}
          elsif($fh == $stderr)
            {$errors .= $line}
        }
     }
 
  #Example 3 (Grab the standard output & standard error of a system call):
 
  use IO::Pipe::Producer;
  $obj = new IO::Pipe::Producer();
  ($stdout_fh,$stderr_fh) =
    $obj->getSystemProducer("echo \"Hello World!\"");

ABSTRACT

Producer.pm is useful for chaining large data processing subroutines or system calls. Instead of making each call serially and waiting for a return, you can create a Producer that will continuously generate output that can be immediately processed. You can even split up input and run subroutines in parallel. Producer.pm is basically a way to pipe the standard output of a forked subroutine or system call to a file handle in your parent process.

DESCRIPTION

Producer.pm is a module that provides methods to fork off a subroutine or system call and return handles on the standard output (STDOUT and STDERR). If you have (for example) a subroutine that processes a very large text file and performs a task on each line, but you need to perform further processing, normally you would have to wait until the subroutine returns to get its output. If the subroutine prints its output to STDOUT (and STDERR) or you can edit it to do so, you can call it using a Producer so that you can use the returned handle to continuously process each line as it's "produced". You can chain subroutines together like this by having your subroutine itself create a Producer. This is similar to using open() to run a system call, except that with this module, you can get a handle on STDERR and use it with subroutines as well. And by dividing up your input, you can take advantage of multi-core systems and process your data in a parallel fashion.

Note that the handles retuned are open file handles. It is your job to close them once you are finished with them.

NOTES

This module was originally written as a simple subroutine that used IO::Pipe. It adds one method and a helper method (Note: The getSystemProducer method calls getSubroutineProducer). It functions by opening STDOUT/STDERR as input, which is the basic definition of a pipe. Those input file handles are what is returned.

BUGS

No known bugs. Please report them to <rleach@princeton.edu> if you find any.

SEE ALSO

IO::Pipe IO::Select

AUTHOR

Robert William Leach, <rleach@princeton.edu>

COPYRIGHT AND LICENSE

This software and ancillary information (herein called "SOFTWARE") called Producer.pm is made available under the terms described here. The SOFTWARE has been approved for release with associated LA-CC number LA-CC-05-060.

Unless otherwise indicated, this software has been authored by an employee or employees of the University of California, operator of the Los Alamos National Laboratory under Contract No. W-7405-ENG-36 with the U.S. Department of Energy. The U.S. government has rights to use, reproduce, and distribute this SOFTWARE. The public may copy, distribute, prepare derivative works and publicly display this SOFTWARE without charge, provided that this notice and any statement of authorship are reproduced on all copies. Neither the government nor the university makes any warranty, express or implied, or assumes any liability or responsibility for the use of this SOFTWARE.

If SOFTWARE is modified to produce derivative works, such modified SOFTWARE should be clearly marked, so as not to confuse it with the version available from LANL.