HADOOP-9267. hadoop -help, -h, --help should show usage instructions. Contributed by Andrew Wang.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1449162 13f79535-47bb-0310-9956-ffa450edef68

hadoop-common-project/hadoop-common/CHANGES.txt

@@ -39,6 +39,9 @@ Release 2.0.4-beta - UNRELEASED
 
     HADOOP-9304. remove addition of avro genreated-sources dirs to build. (tucu)
 
+    HADOOP-9267. hadoop -help, -h, --help should show usage instructions.
+    (Andrew Wang via atm)
+
 Release 2.0.3-alpha - 2013-02-06 
 
   INCOMPATIBLE CHANGES

hadoop-common-project/hadoop-common/src/main/bin/hadoop

@@ -50,6 +50,12 @@ fi
 
 COMMAND=$1
 case $COMMAND in
+  # usage flags
+  --help|-help|-h)
+    print_usage
+    exit
+    ;;
+
   #hdfs commands
   namenode|secondarynamenode|datanode|dfs|dfsadmin|fsck|balancer|fetchdt|oiv|dfsgroups)
     echo "DEPRECATED: Use of this script to execute hdfs command is deprecated." 1>&2

hadoop-hdfs-project/hadoop-hdfs/src/main/bin/hdfs

@@ -56,6 +56,14 @@ fi
 COMMAND=$1
 shift
 
+case $COMMAND in
+  # usage flags
+  --help|-help|-h)
+    print_usage
+    exit
+    ;;
+esac
+
 # Determine if we're starting a secure datanode, and if so, redefine appropriate variables
 if [ "$COMMAND" == "datanode" ] && [ "$EUID" -eq 0 ] && [ -n "$HADOOP_SECURE_DN_USER" ]; then
   if [ -n "$JSVC_HOME" ]; then

hadoop-yarn-project/hadoop-yarn/bin/yarn

@@ -53,13 +53,7 @@ DEFAULT_LIBEXEC_DIR="$bin"/../libexec
 HADOOP_LIBEXEC_DIR=${HADOOP_LIBEXEC_DIR:-$DEFAULT_LIBEXEC_DIR}
 . $HADOOP_LIBEXEC_DIR/yarn-config.sh
 
-cygwin=false
+function print_usage(){
-case "`uname`" in
-CYGWIN*) cygwin=true;;
-esac
-
-# if no args specified, show usage
-if [ $# = 0 ]; then
   echo "Usage: yarn [--config confdir] COMMAND"
   echo "where COMMAND is one of:"
   echo "  resourcemanager      run the ResourceManager" 
@@ -76,6 +70,16 @@ if [ $# = 0 ]; then
   echo " or"
   echo "  CLASSNAME            run the class named CLASSNAME"
   echo "Most commands print help when invoked w/o parameters."
+}
+
+cygwin=false
+case "`uname`" in
+CYGWIN*) cygwin=true;;
+esac
+
+# if no args specified, show usage
+if [ $# = 0 ]; then
+  print_usage
   exit 1
 fi
 
@@ -83,6 +87,14 @@ fi
 COMMAND=$1
 shift
 
+case $COMMAND in
+  # usage flags
+  --help|-help|-h)
+    print_usage
+    exit
+    ;;
+esac
+
 if [ -f "${YARN_CONF_DIR}/yarn-env.sh" ]; then
   . "${YARN_CONF_DIR}/yarn-env.sh"
 fi