Getting hadoop pipes to work on os x with file access - c++

Question

my apologies if this question is trivial, but I haven't been able to solve it properly despite spending a few hours on google…
I have compiled and installed hadoop 2.5.2 from source on OS X 10.8. I think all went well with this, even though getting the native libraries compiled was a bit of a pain.
To verify my installation, I tried the examples that ship with hadoop like this:
$ hadoop jar /Users/per/source/hadoop-2.5.2-src/hadoop-dist/target/hadoop-2.5.2/share/hadoop/mapreduce/hadoop-mapreduce-examples-2.5.2.jar pi 2 5
which gives me back
Job Finished in 1.774 seconds
Estimated value of Pi is 3.60000000000000000000
So that seems to indicate that hadoop is at least working, I think.
Since my end goal is to get this working with file I/O from a C++ program using pipes, I also did try the following as an intermediate step:
$ hdfs dfs -put etc/hadoop input
$ hadoop jar share/hadoop/mapreduce/hadoop-mapreduce-examples-2.5.2.jar grep input output 'dfs[a-z.]+'
Which also seems to work (as in producing the correct output).
Then, finally, I tried the wordcount.cpp example, and this is not working, although I fail to understand how to fix it. The error message is quite clear.
2015-10-21 13:38:33,539 WARN org.apache.hadoop.security.UserGroupInformation: No groups available for user per
2015-10-21 13:38:33,678 INFO org.apache.hadoop.security.JniBasedUnixGroupsMapping: Error getting groups for per: getgrouplist: error looking up group. 5 (Input/output error)
So obviously there is something I don't get with the file permissions, but what? My hdfs-site.xml file looks like this, where I have tried to turn off permissions checks altogether.
<configuration>
<property>
<name>dfs.replication</name>
<value>1</value>
</property>
<property>
<name>dfs.web.ugi</name>
<value>per</value>
</property>
<property>
<name>dfs.permissions</name>
<value>false</value>
</property>
</configuration>
But I am confused since I at least seem to be able to use grep on files in hdfs (per the built-in example above).
Any feedback would be greatly appreciated. I am running all of this as myself, so I haven't created a new user for only hadoop, since I am only running it locally on my laptop for now.
Edit: Update with some additional output from my terminal window, according to the discussion below:
<snip>
15/10/21 14:47:41 INFO mapred.MapTask: bufstart = 0; bufvoid = 104857600
15/10/21 14:47:41 INFO mapred.MapTask: kvstart = 26214396; length = 6553600
15/10/21 14:47:41 INFO mapred.LocalJobRunner: map task executor complete.
15/10/21 14:47:41 WARN mapred.LocalJobRunner: job_local676909674_0001
java.lang.Exception: java.lang.NullPointerException
at org.apache.hadoop.mapred.LocalJobRunner$Job.runTasks(LocalJobRunner.java:462)
at org.apache.hadoop.mapred.LocalJobRunner$Job.run(LocalJobRunner.java:522)
Caused by: java.lang.NullPointerException
at org.apache.hadoop.mapred.pipes.Application.<init>(Application.java:104)
at org.apache.hadoop.mapred.pipes.PipesMapRunner.run(PipesMapRunner.java:69)
at org.apache.hadoop.mapred.MapTask.runOldMapper(MapTask.java:430)
at org.apache.hadoop.mapred.MapTask.run(MapTask.java:342)
<snip>
I can add more if that is relevant