bin=`dirname "$0"`
bin=`cd "$bin">/dev/null; pwd`
# This will set HBASE_HOME, etc.
. "$bin"/hbase-config.sh
#判断cygwin
cygwin=false
case "`uname`" in
CYGWIN*) cygwin=true;;
esac
#是否是开发环境
# Detect if we are in hbase sources dir
in_dev_env=false
if [ -d "${HBASE_HOME}/target" ]; then
  in_dev_env=true
fi
#省去参数判断
#获取命令
# get arguments
COMMAND=$1
shift
JAVA=$JAVA_HOME/bin/java
#去除加载文件
#加载jruby 文件
# check if the commmand needs jruby
declare -a jruby_cmds=("shell" "org.jruby.Main")
for cmd in "${jruby_cmds[@]}"; do
  if [[ $cmd == "$COMMAND" ]]; then
    jruby_needed=true
    break
  fi
done
# the command needs jrub

计算命令执行那些东西
# figure out which class to run
if [ "$COMMAND" = "shell" ] ; then
	#find the hbase ruby sources
  if [ -d "$HBASE_HOME/lib/ruby" ]; then
    HBASE_OPTS="$HBASE_OPTS -Dhbase.ruby.sources=$HBASE_HOME/lib/ruby"
  else
    HBASE_OPTS="$HBASE_OPTS -Dhbase.ruby.sources=$HBASE_HOME/hbase-shell/src/main/ruby"
  fi
  HBASE_OPTS="$HBASE_OPTS $HBASE_SHELL_OPTS"
  CLASS="org.jruby.Main -X+O ${JRUBY_OPTS} ${HBASE_HOME}/bin/hirb.rb"
elif [ "$COMMAND" = "hbck" ] ; then
  CLASS='org.apache.hadoop.hbase.util.HBaseFsck'
# TODO remove old 'hlog' version
elif [ "$COMMAND" = "hlog" -o "$COMMAND" = "wal" ] ; then
  CLASS='org.apache.hadoop.hbase.wal.WALPrettyPrinter'
elif [ "$COMMAND" = "hfile" ] ; then
  CLASS='org.apache.hadoop.hbase.io.hfile.HFilePrettyPrinter'
elif [ "$COMMAND" = "zkcli" ] ; then
  CLASS="org.apache.hadoop.hbase.zookeeper.ZooKeeperMainServer"
elif [ "$COMMAND" = "backup" ] ; then
  CLASS='org.apache.hadoop.hbase.backup.BackupDriver'
elif [ "$COMMAND" = "restore" ] ; then
  CLASS='org.apache.hadoop.hbase.backup.RestoreDriver'
elif [ "$COMMAND" = "upgrade" ] ; then
  echo "This command was used to upgrade to HBase 0.96, it was removed in HBase 2.0.0."
  echo "Please follow the documentation at http://hbase.apache.org/book.html#upgrading."
  exit 1
elif [ "$COMMAND" = "snapshot" ] ; then
  SUBCOMMAND=$1
  shift
  if [ "$SUBCOMMAND" = "create" ] ; then
    CLASS="org.apache.hadoop.hbase.snapshot.CreateSnapshot"
  elif [ "$SUBCOMMAND" = "info" ] ; then
    CLASS="org.apache.hadoop.hbase.snapshot.SnapshotInfo"
  elif [ "$SUBCOMMAND" = "export" ] ; then
    CLASS="org.apache.hadoop.hbase.snapshot.ExportSnapshot"
  else
    echo "Usage: hbase [<options>] snapshot <subcommand> [<args>]"
    echo "$options_string"
    echo ""
    echo "Subcommands:"
    echo "  create          Create a new snapshot of a table"
    echo "  info            Tool for dumping snapshot information"
    echo "  export          Export an existing snapshot"
    exit 1
  fi
elif [ "$COMMAND" = "master" ] ; then
  CLASS='org.apache.hadoop.hbase.master.HMaster'
  if [ "$1" != "stop" ] && [ "$1" != "clear" ] ; then
    HBASE_OPTS="$HBASE_OPTS $HBASE_MASTER_OPTS"
  fi
elif [ "$COMMAND" = "regionserver" ] ; then
  CLASS='org.apache.hadoop.hbase.regionserver.HRegionServer'
  if [ "$1" != "stop" ] ; then
    HBASE_OPTS="$HBASE_OPTS $HBASE_REGIONSERVER_OPTS"
  fi
elif [ "$COMMAND" = "thrift" ] ; then
  CLASS='org.apache.hadoop.hbase.thrift.ThriftServer'
  if [ "$1" != "stop" ] ; then
    HBASE_OPTS="$HBASE_OPTS $HBASE_THRIFT_OPTS"
  fi
elif [ "$COMMAND" = "thrift2" ] ; then
  CLASS='org.apache.hadoop.hbase.thrift2.ThriftServer'
  if [ "$1" != "stop" ] ; then
    HBASE_OPTS="$HBASE_OPTS $HBASE_THRIFT_OPTS"
  fi
elif [ "$COMMAND" = "rest" ] ; then
  CLASS='org.apache.hadoop.hbase.rest.RESTServer'
  if [ "$1" != "stop" ] ; then
    HBASE_OPTS="$HBASE_OPTS $HBASE_REST_OPTS"
  fi
elif [ "$COMMAND" = "zookeeper" ] ; then
  CLASS='org.apache.hadoop.hbase.zookeeper.HQuorumPeer'
  if [ "$1" != "stop" ] ; then
    HBASE_OPTS="$HBASE_OPTS $HBASE_ZOOKEEPER_OPTS"
  fi
elif [ "$COMMAND" = "clean" ] ; then
  case $1 in
    --cleanZk|--cleanHdfs|--cleanAll) 
      matches="yes" ;;
    *) ;;
  esac
  if [ $# -ne 1 -o "$matches" = "" ]; then
    echo "Usage: hbase clean (--cleanZk|--cleanHdfs|--cleanAll)"
    echo "Options: "
    echo "        --cleanZk   cleans hbase related data from zookeeper."
    echo "        --cleanHdfs cleans hbase related data from hdfs."
    echo "        --cleanAll  cleans hbase related data from both zookeeper and hdfs."
    exit 1;
  fi
  "$bin"/hbase-cleanup.sh --config ${HBASE_CONF_DIR} $@
  exit $
elif [ "$COMMAND" = "mapredcp" ] ; then
  CLASS='org.apache.hadoop.hbase.util.MapreduceDependencyClasspathTool'
elif [ "$COMMAND" = "classpath" ] ; then
  echo $CLASSPATH
  exit 0
elif [ "$COMMAND" = "pe" ] ; then
  CLASS='org.apache.hadoop.hbase.Performanceeva luation'
  HBASE_OPTS="$HBASE_OPTS $HBASE_PE_OPTS"
elif [ "$COMMAND" = "ltt" ] ; then
  CLASS='org.apache.hadoop.hbase.util.LoadTestTool'
  HBASE_OPTS="$HBASE_OPTS $HBASE_LTT_OPTS"
elif [ "$COMMAND" = "canary" ] ; then
  CLASS='org.apache.hadoop.hbase.tool.Canary'
  HBASE_OPTS="$HBASE_OPTS $HBASE_CANARY_OPTS"
elif [ "$COMMAND" = "version" ] ; then
  CLASS='org.apache.hadoop.hbase.util.VersionInfo'
else
  CLASS=$COMMAND
fi
# Have JVM dump heap if we run out of memory.  Files will be 'launch directory'
# and are named like the following: java_pid21612.hprof. Apparently it doesn't
# 'cost' to have this flag enabled. Its a 1.6 flag only. See:
# http://blogs.sun.com/alanb/entry/outofmemoryerror_looks_a_bit_better
HBASE_OPTS="$HBASE_OPTS -Dhbase.log.dir=$HBASE_LOG_DIR"
HBASE_OPTS="$HBASE_OPTS -Dhbase.log.file=$HBASE_LOGFILE"
HBASE_OPTS="$HBASE_OPTS -Dhbase.home.dir=$HBASE_HOME"
HBASE_OPTS="$HBASE_OPTS -Dhbase.id.str=$HBASE_IDENT_STRING"
HBASE_OPTS="$HBASE_OPTS -Dhbase.root.logger=${HBASE_ROOT_LOGGER:-INFO,console}"
if [ "x$JAVA_LIBRARY_PATH" != "x" ]; then
  HBASE_OPTS="$HBASE_OPTS -Djava.library.path=$JAVA_LIBRARY_PATH"
  export LD_LIBRARY_PATH="$LD_LIBRARY_PATH:$JAVA_LIBRARY_PATH"
fi
# Enable security logging on the master and regionserver only
if [ "$COMMAND" = "master" ] || [ "$COMMAND" = "regionserver" ]; then
  HBASE_OPTS="$HBASE_OPTS -Dhbase.security.logger=${HBASE_SECURITY_LOGGER:-INFO,RFAS}"
else
  HBASE_OPTS="$HBASE_OPTS -Dhbase.security.logger=${HBASE_SECURITY_LOGGER:-INFO,NullAppender}"
fi
HEAP_SETTINGS="$JAVA_HEAP_MAX $JAVA_OFFHEAP_MAX"
# Exec unless HBASE_NOEXEC is set.
export CLASSPATH
if [ "${HBASE_NOEXEC}" != "" ]; then
  "$JAVA" -Dproc_$COMMAND -XX:OnOutOfMemoryError="kill -9 %p" $HEAP_SETTINGS $HBASE_OPTS $CLASS "$@"
else
  exec "$JAVA" -Dproc_$COMMAND -XX:OnOutOfMemoryError="kill -9 %p" $HEAP_SETTINGS $HBASE_OPTS $CLASS "$@"
fi
最后执行Java类
COMMAND ： start/stop/restart
OnOutOfMemoryError ： 当内存溢出时直接杀死进程
HEAP_SETTINGS ：设置最大堆，
CLASS ：这个就是org.apache.hadoop.hbase.regionserver.HRegionServer 等。