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--- courses:mapreduce-tutorial:step-3 [2012/01/29 23:22]
majlis
+++ courses:mapreduce-tutorial:step-3 [2012/01/31 09:40] (current)
straka Change Perl commandline syntax.
@@ Line 8: / Line 8: @@
 <file perl>
-package Mapper;
+package My::Mapper;
 use Moose;
 with 'Hadoop::Mapper';
@@ Line 18: / Line 18: @@
 }
-package Main;
+package main;
 use Hadoop::Runner;
 my $runner = Hadoop::Runner->new(
-  mapper => Mapper->new(),
+  mapper => My::Mapper->new(),
   input_format => 'TextInputFormat',
   output_format => 'TextOutputFormat',
@@ Line 33: / Line 33: @@
 Resulting script can be executed locally in a single thread using
-  perl script.pl run input_directory output_directory
+  perl script.pl input output_directory
-All files in input_directory are processes. The output_directory must not exist.
+Input can be either file or a directory -- in that case, all files in this directory are processes. The output_directory must not exist.
+=== Standard input and output ===
+Standard input and standard output of the Perl script are used to communicate with the Hadoop framework. Therefore you should use standard error output if you want to print some debugging output using ''print STDERR "Message"''.
 ===== Exercise =====
@@ Line 41: / Line 43: @@
 To check that your Hadoop environment works, try running a MR job on ''/home/straka/wiki/cs-text-medium'', which outputs only articles with names beginning with an ''A'' (ignoring the case). You can download the template {{:courses:mapreduce-tutorial:step-3-exercise.txt|step-3-exercise.pl}}  and execute it.
   wget --no-check-certificate 'https://wiki.ufal.ms.mff.cuni.cz/_media/courses:mapreduce-tutorial:step-3-exercise.txt' -O 'step-3-exercise.pl'
-  rm -rf step-3-out-ex; perl step-3-exercise.pl run /home/straka/wiki/cs-text-medium/ step-3-out-ex
+  # NOW EDIT THE FILE
+  # $EDITOR step-3-exercise.pl
+  rm -rf step-3-out-ex; perl step-3-exercise.pl /home/straka/wiki/cs-text-medium/ step-3-out-ex
   less step-3-out-ex/part-*
@@ Line 47: / Line 51: @@
 You can also download the solution {{:courses:mapreduce-tutorial:step-3-solution.txt|step-3-solution.pl}} and check the correct output.
   wget --no-check-certificate 'https://wiki.ufal.ms.mff.cuni.cz/_media/courses:mapreduce-tutorial:step-3-solution.txt' -O 'step-3-solution.pl'
-  rm -rf step-3-out-sol; perl step-3-solution.pl run /home/straka/wiki/cs-text-medium/ step-3-out-sol
+  # NOW VIEW THE FILE
+  # $EDITOR step-3-solution.pl
+  rm -rf step-3-out-sol; perl step-3-solution.pl /home/straka/wiki/cs-text-medium/ step-3-out-sol
   less step-3-out-sol/part-*

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