NAME

    Process::Pipeline - execute processes as pipeline

SYNOPSIS

    In shell:

       $ zcat access.log.gz | grep -v 127.0.0.1 | grep -c POST

    In perl5:

      use Process::Pipeline;
    
      my $pipeline = Process::Pipeline->new
        ->push(sub { my $p = shift; $p->cmd("zcat", "access.log.gz")   })
        ->push(sub { my $p = shift; $p->cmd("grep", "-v", "127.0.0.1") })
        ->push(sub { my $p = shift; $p->cmd("grep", "-c", "POST"       });
    
      my $r = $pipeline->start;
      if ($r->is_success) {
         my $fh = $result->fh; # output filehandle of $pipeline
         say <$fh>;
      }

    In perl5 with DSL:

      use Process::Pipeline::DSL;
    
      my $pipeline = proc { "zcat", "access.log.gz"   }
                     proc { "grep", "-v", "127.0.0.1" }
                     proc { "grep", "-c", "POST"      };
    
      my $r = $pipeline->start;
      if ($r->is_success) {
         my $fh = $result->fh; # output filehandle of $pipeline
         say <$fh>;
      }

DESCRIPTION

    Process::Pipeline helps you write a pipeline of processes.

MOTIVATION

    It is known that we should avoid shell-invocation in perl. But, because
    the notation of shell is very convenient, I sometimes find myself
    invoking shell. Oops.

    The main reason for invoking shell in perl is that perl does not have
    as convenient notation as shell has.

    Process::Pipeline try to give an easy pipeline notation to perl. Why
    don't you change

        chomp(my $num = `zcat access.log.gz | grep -v 127.0.0.1 | grep -c POST`);

    into

        use Process::Pipeline::DSL;
        my $p = proc { "zcat", "access.log.gz"   }
                proc { "grep", "-v", "127.0.0.1" }
                proc { "grep", "-c", "POST"      };
        my $r = $p->start;
        if ($r->is_success) {
          my $fh = $r->fh;
          chomp(my $num = <$fh>);
        }

METHODS

 new

      my $pipeline = Process::Pipeline->new;

    Constructor.

 push

      $pipeline->push(sub {
        my $p = shift;
        $p->cmd("zcat", "access.log.gz");
      });
      $pipeline->push(sub {
        my $p = shift;
        $p->set("2>", "/dev/null");
        $p->cmd("zcat", "access.log.gz");
      });

    Push a Process::Pipeline::Process object to the pipeline.

  start

       my $result = $pipeline->start;

    Start the pipeline. It returns a Process::Pipeline::Result object.

       my $result = $pipeline->start;
       my $bool   = $reuslt->is_success; # all commands exit successfully
       my $fh     = $reuslt->fh;         # pipeline's output filehandle

DSL

    There is a DSL for Process::Pipeline. Process::Pipeline::DSL exports
    proc and set functions, and you can construct pipelines easily.

      use Process::Pipeline::DSL;
      my $p = proc { "git", "archive", "--format=tar", "--prefix=repo/", "HEAD" }
              proc { set ">" => "repo.tar.gz"; "gzip" };
      my $r = $p->start;

COPYRIGHT AND LICENSE

    Copyright 2016 Shoichi Kaji <skaji@cpan.org>

    This library is free software; you can redistribute it and/or modify it
    under the same terms as Perl itself.