Package org.apache.zookeeper

Class Shell

  • Direct Known Subclasses:
    Shell.ShellCommandExecutor
    public abstract class Shell
extends java.lang.Object
    A base class for running a Unix command. Shell can be used to run unix commands like du or df. It also offers facilities to gate commands by time-intervals.

    • Field Summary

      Fields 
      Modifier and Type Field Description
      static java.lang.String SET_GROUP_COMMAND  
      static java.lang.String SET_OWNER_COMMAND
      a Unix command to set owner
      static java.lang.String SET_PERMISSION_COMMAND
      a Unix command to set permission
      protected long timeOutInterval
      Time after which the executing script would be timedout
      static java.lang.String ULIMIT_COMMAND
      a Unix command to get ulimit of a process.
      static java.lang.String USER_NAME_COMMAND
      a Unix command to get the current user's name
      static boolean WINDOWS
      Set to true on Windows platforms

    • Constructor Summary

      Constructors 
      Constructor Description
      Shell()  
      Shell​(long interval)  

    • Method Summary

      All Methods Static Methods Instance Methods Abstract Methods Concrete Methods 
      Modifier and Type Method Description
      static java.lang.String execCommand​(java.lang.String... cmd)
      Static method to execute a shell command.
      static java.lang.String execCommand​(java.util.Map<java.lang.String,​java.lang.String> env, java.lang.String... cmd)
      Static method to execute a shell command.
      static java.lang.String execCommand​(java.util.Map<java.lang.String,​java.lang.String> env, java.lang.String[] cmd, long timeout)
      Static method to execute a shell command.
      protected abstract java.lang.String[] getExecString()
      return an array containing the command name & its parameters
      int getExitCode()
      get the exit code
      static java.lang.String[] getGET_PERMISSION_COMMAND()
      Return a Unix command to get permission information.
      static java.lang.String[] getGroupsCommand()
      a Unix command to get the current user's groups list
      static java.lang.String[] getGroupsForUserCommand​(java.lang.String user)
      a Unix command to get a given user's groups list
      java.lang.Process getProcess()
      get the current sub-process executing the given command
      static java.lang.String[] getUlimitMemoryCommand​(int memoryLimit)
      Get the Unix command for setting the maximum virtual memory available to a given child process.
      boolean isTimedOut()
      To check if the passed script to shell command executor timed out or not.
      protected abstract void parseExecResult​(java.io.BufferedReader lines)
      Parse the execution result
      protected void run()
      check to see if a command needs to be executed and execute if needed
      protected void setEnvironment​(java.util.Map<java.lang.String,​java.lang.String> env)
      set the environment for the command
      protected void setWorkingDirectory​(java.io.File dir)
      set the working directory

      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

    • Field Detail

      • USER_NAME_COMMAND

        public static final java.lang.String USER_NAME_COMMAND
        a Unix command to get the current user's name
        See Also:
        Constant Field Values

      • SET_PERMISSION_COMMAND

        public static final java.lang.String SET_PERMISSION_COMMAND
        a Unix command to set permission
        See Also:
        Constant Field Values

      • SET_OWNER_COMMAND

        public static final java.lang.String SET_OWNER_COMMAND
        a Unix command to set owner
        See Also:
        Constant Field Values

      • SET_GROUP_COMMAND

        public static final java.lang.String SET_GROUP_COMMAND
        See Also:
        Constant Field Values

      • timeOutInterval

        protected long timeOutInterval
        Time after which the executing script would be timedout

      • ULIMIT_COMMAND

        public static final java.lang.String ULIMIT_COMMAND
        a Unix command to get ulimit of a process.
        See Also:
        Constant Field Values

      • WINDOWS

        public static final boolean WINDOWS
        Set to true on Windows platforms

    • Constructor Detail

      • Shell

        public Shell()

      • Shell

        public Shell​(long interval)
        Parameters:
        interval - the minimum duration to wait before re-executing the command.

    • Method Detail

      • getGroupsCommand

        public static java.lang.String[] getGroupsCommand()
        a Unix command to get the current user's groups list

      • getGroupsForUserCommand

        public static java.lang.String[] getGroupsForUserCommand​(java.lang.String user)
        a Unix command to get a given user's groups list

      • getGET_PERMISSION_COMMAND

        public static java.lang.String[] getGET_PERMISSION_COMMAND()
        Return a Unix command to get permission information.

      • getUlimitMemoryCommand

        public static java.lang.String[] getUlimitMemoryCommand​(int memoryLimit)
        Get the Unix command for setting the maximum virtual memory available to a given child process. This is only relevant when we are forking a process from within the Mapper or the Reducer implementations. Also see Hadoop Pipes and Hadoop Streaming. It also checks to ensure that we are running on a *nix platform else (e.g. in Cygwin/Windows) it returns null.
        Parameters:
        memoryLimit - virtual memory limit
        Returns:
        a String[] with the ulimit command arguments or null if we are running on a non *nix platform or if the limit is unspecified.

      • setEnvironment

        protected void setEnvironment​(java.util.Map<java.lang.String,​java.lang.String> env)
        set the environment for the command
        Parameters:
        env - Mapping of environment variables

      • setWorkingDirectory

        protected void setWorkingDirectory​(java.io.File dir)
        set the working directory
        Parameters:
        dir - The directory where the command would be executed

      • run

        protected void run()
            throws java.io.IOException
        check to see if a command needs to be executed and execute if needed
        Throws:
        java.io.IOException

      • getExecString

        protected abstract java.lang.String[] getExecString()
        return an array containing the command name & its parameters

      • parseExecResult

        protected abstract void parseExecResult​(java.io.BufferedReader lines)
                                 throws java.io.IOException
        Parse the execution result
        Throws:
        java.io.IOException

      • getProcess

        public java.lang.Process getProcess()
        get the current sub-process executing the given command
        Returns:
        process executing the command

      • getExitCode

        public int getExitCode()
        get the exit code
        Returns:
        the exit code of the process

      • isTimedOut

        public boolean isTimedOut()
        To check if the passed script to shell command executor timed out or not.
        Returns:
        if the script timed out.

      • execCommand

        public static java.lang.String execCommand​(java.lang.String... cmd)
                                    throws java.io.IOException
        Static method to execute a shell command. Covers most of the simple cases without requiring the user to implement the Shell interface.
        Parameters:
        cmd - shell command to execute.
        Returns:
        the output of the executed command.
        Throws:
        java.io.IOException

      • execCommand

        public static java.lang.String execCommand​(java.util.Map<java.lang.String,​java.lang.String> env,
                                           java.lang.String[] cmd,
                                           long timeout)
                                    throws java.io.IOException
        Static method to execute a shell command. Covers most of the simple cases without requiring the user to implement the Shell interface.
        Parameters:
        env - the map of environment key=value
        cmd - shell command to execute.
        timeout - time in milliseconds after which script should be marked timeout
        Returns:
        the output of the executed command.o
        Throws:
        java.io.IOException

      • execCommand

        public static java.lang.String execCommand​(java.util.Map<java.lang.String,​java.lang.String> env,
                                           java.lang.String... cmd)
                                    throws java.io.IOException
        Static method to execute a shell command. Covers most of the simple cases without requiring the user to implement the Shell interface.
        Parameters:
        env - the map of environment key=value
        cmd - shell command to execute.
        Returns:
        the output of the executed command.
        Throws:
        java.io.IOException