[Hadoop Wiki] Update of "UnixShellScriptProgrammingGuide" by SomeOtherAccount

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The "UnixShellScriptProgrammingGuide" page has been changed by SomeOtherAccount:
https://wiki.apache.org/hadoop/UnixShellScriptProgrammingGuide?action=diff&rev1=16&rev2=17

  
  1-... unless `HADOOP_IDENT_STRING` is modified appropriately. This means that post-HADOOP-9902, it is now possible to run two secure datanodes on the same machine as the same user, since all of the logs, pids, and outs, take that into consideration! QA folks should be very happy.
  
+ = A New Subproject or Subproject-like Structure =
+ 
+ The following files should be the basis of the new bits:
+ 
+ * libexec/(project)-config.sh
+ 
+ This contains the new, common configuration/startup bits. At a minimum, it should contain the bootstrap stanza for hadoop-config.sh and a function called hadoop_subproject_init that does the actual, extra work that needs to be done.  Variables should be HADOOP_(project)_(whatever) and should be initialized based off of the standard HADOOP_* variables.
+ 
+ * bin/(project) or sbin/(project)
+ 
+ User-facing commands, those should be in bin.  Administrator commands should be in sbin.  See the skeleton example up above on how to build these types of scripts.
+ 
+ * conf/*-env.sh
+ 
+ Ideally, this should follow the pattern already established by the other *-env.sh files.  Entries in it can also be in hadoop-env.sh to provide for a consistent and much easier operational experience.
+