/ 
Process-Pipeline-0.04
River stage zero No dependents
/ Process::Pipeline

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 $result = $pipeline->start;
if ($result->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 $result = $pipeline->start;
if ($result->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.