Accessing HBase by using the HBase Shell
After you have started HBase, you can access the database in an interactive way by using the HBase Shell, which is a command interpreter for HBase which is written in Ruby.
$ hbase shell
Setting Virtual Machine Options for HBase Shell
HBase in CDH 5.2 and newer allows you to set variables for the virtual machine running HBase Shell, by using the HBASE_SHELL_OPTS environment variable. This example sets several options in the virtual machine.
$ HBASE_SHELL_OPTS="-verbose:gc -XX:+PrintGCApplicationStoppedTime -XX:+PrintGCDateStamps -XX:+PrintGCDetails -Xloggc:$HBASE_HOME/logs/gc-hbase.log" ./bin/hbase shell
Scripting with HBase Shell
A new feature of HBase Shell in CDH 5.2 is non-interactive mode. This mode allows you to use HBase Shell in scripts, and allow the script to access the exit status of the HBase Shell commands. To invoke non-interactive mode, use the -n or --non-interactive switch. This small example script shows how to use HBase Shell in a Bash script.
#!/bin/bash echo 'list' | hbase shell -n status=$? if [$status -ne 0]; then echo "The command may have failed." fi
Successful HBase Shell commands return an exit status of 0. However, an exit status other than 0 does not necessarily indicate a failure, but should be interpreted as unknown. For example, a command may succeed, but while waiting for the response, the client may lose connectivity. In that case, the client has no way to know the outcome of the command. In the case of a non-zero exit status, your script should check to be sure the command actually failed before taking further action.
You can also write Ruby scripts for use with HBase Shell. Example Ruby scripts are included in the hbase-examples/src/main/ruby/ directory.