/ 
Pipe-0.02
River stage one • 1 direct dependent • 1 total dependent
/ Pipe

NAME

Pipe - Framework to create pipes using iterators

SYNOPSIS

use Pipe;
my @input = Pipe->cat("t/data/file1", "t/data/file2");
my @lines = Pipe->cat("t/data/file1", "t/data/file2")->chomp;
my @uniqs = Pipe->cat("t/data/file1", "t/data/file2")->chomp->uniq;

Pipe->cat("t/data/file1", "t/data/file2")->uniq->print("t/data/out");

WARNING

This is Alpha version. The user API might still change

DESCRIPTION

Building an iterating pipe with prebuilt and home made tubes.

Tubes available in this distibution:

cat

Read in the lines of one or more file.

chomp

Remove trailing newlines from each line.

find

Pipe->find(".")

Returns every file, directory, etc. under the directory tree passed to it.

for

Pipe->for(@array)

Iterates over the elements of an array. Basically the same as the for or foreach loop of Perl.

glob

Implements the Perl glob function.

grep

Selectively pass on values.

Can be used either with a regex:

->grep( qr/regex/ )

Or with a sub:

->grep( sub { length($_[0]) > 12 } )

Very similar to the built-in grep command of Perl but instead of regex you have to pass a compiled regex using qr// and instead of a block you have to pass an anonymous sub {}

map

Similar to the Perl map construct, except that instead of a block you pass an anonymous function sub {}.

->map(  sub {  length $_[0] } );

print

TODO Not implemented yet

Prints out its input. By default it prints to STDOUT but the user can supply a filename or a filehandle.

Pipe->cat("t/data/file1", "t/data/file2")->print;
Pipe->cat("t/data/file1", "t/data/file2")->print("out.txt");
Pipe->cat("t/data/file1", "t/data/file2")->print(':a', "out.txt");

say

It is the same as print but adds a newline at the end of each line. The name is Perl6 native.

sort

Similar to the built in sort function of Perl. As sort needs to have all the data in the memory, once you use sort in the Pipe it stops being an iterator for the rest of the pipe.

By default it sorts based on ascii table but you can provide your own sorting function. The two values to be compared are passed to this function.

Pipe->cat("t/data/numbers1")->chomp->sort( sub { $_[0] <=> $_[1] } );

tuple

Given one or more array references, on every iteration it will return an n-tuple (n is the number of arrays), one value from each source array.

my @a = qw(foo bar baz moo);
my @b = qw(23  37  77  42);

my @one_tuple = Pipe->tuple(\@a);
# @one_tuple is ['foo'], ['bar'], ['baz'], ['moo']

my @two_tuple = Pipe->tuple(\@a, \@b);
# @two_tuple is ['foo', 23], ['bar', 37], ['baz', 77], ['moo', 42]

Input: disregards any input so it can be used as a starting element of a Pipe

Ouput: array refs of n elements

uniq

Similary to the unix uniq command eliminate duplicate consecutive values.

23, 23, 19, 23 becomes 23, 19, 23

Warning: as you can see from the example this method does not give real unique values, it only eliminates consecutive duplicates.

Building your own tube

If you would like to build a tube called "thing" create a module called Pipe::Tube::Thing that inherits from Pipe::Tube, our abstract Tube.

Implement one or more of these methods in your subclass as you please.

init

Will be called once when initializing the pipeline. It will get ($self, @args) where $self is the Pipe::Tube::Thing object and @args are the values given as parameters to the ->thing(@args) call in the pipeline.

run

Will be called every time the previous tube in the pipe returns one or more values. It can return a list of values that will be passed on to the next tube. If based on the current state of Thing there is nothing to do you should call return; with no parameters.

finish

Will be called once when the Pipe Manager notices that this Thing should be finished. This happens when Thing is the first active element in the pipe (all the previous tubes have already finshed) and its run() method returns an empty list.

The finish() method should return a list of values that will be passed on to the next tube in the pipe. This is especially useful for Tubes such as sort that can to their thing only after they have received all the input.

Debugging your tube

You can call $self->logger("some message") from your tube. It will be printed to pipe.log if someone sets $Pipe::DEBUG = 1;

Examples

A few examples of UNIX Shell commands combined with pipelines

  • cat several files together

    UNIX:

    cat file1 file2 > filenew

    Perl:

    open my $out, ">", "filenew" or die $!;
while (<>) {
   print $out $_;
}

    Perl with Pipe:

    perl -MPipe 'Pipe->cat(@ARG)->print("filenew")'

  • UNIX:

    grep REGEX file* | uniq

    Perl:

    my $last;
while (<>) {
   next if not /REGEX/;

   if (not defined $last) {
       $last = $_;
       print;
       next;
   }
   next if $last eq $_;
   $last = $_;
   print;
}

    Perl with Pipe:

    one of these will work, we hope:

    Pipe->grep(qr/REGEX/, <file*>)->uniq->print
Pipe->cat(<file*>)->grep(qr/REGEX/)->uniq->print
Pipe->files("file*")->cat->grep(qr/REGEX/)->uniq->print

  • UNIX:

    find / -name filename -print

    Perl with Pipe:

    perl -MPipe -e'Pipe->find("/")->grep(qr/filename/)->print'

  • Delete all the CVS directories in a directory tree (from the journal of brian_d_foy) http://use.perl.org/~brian_d_foy/journal/29267

    UNIX:

    find . -name CVS | xargs rm -rf

find . -name CVS -type d -exec rm -rf '{}' \;

    Perlish:

    find2perl . -name CVS -type d -exec rm -rf '{}' \; > rm-cvs.pl
perl rm-cvs.pl

    Perl with Pipe:

    perl -MPipe -e'Pipe->find(".")->grep(qr/^CVS$/)->rmtree;

BUGS

Probably plenty but nothing I know of. Please report them to the author.

Development

The Subversion repository is here: http://svn1.hostlocal.com/szabgab/trunk/Pipe/

Thanks

to Gaal Yahas

AUTHOR

Gabor Szabo <gabor@pti.co.il>

Copyright

Copyright 2006 by Gabor Szabo <gabor@pti.co.il>.

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

See http://www.perl.com/perl/misc/Artistic.html

See Also

Shell::Autobox