Shell (Apache ZooKeeper - Server 3.8.1 API)

java.lang.Object
- org.apache.zookeeper.Shell

Direct Known Subclasses:

Shell.ShellCommandExecutor
```
public abstract class Shell
extends 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.

Nested Class Summary

Nested Classes
Modifier and Type	Class and Description
`static class`	`Shell.ExitCodeException` This is an IOException with exit code added.
`static class`	`Shell.ShellCommandExecutor` A simple shell command executor.

Field Summary

Fields
Modifier and Type	Field and Description
`static String`	`SET_GROUP_COMMAND`
`static String`	`SET_OWNER_COMMAND` a Unix command to set owner
`static String`	`SET_PERMISSION_COMMAND` a Unix command to set permission
`protected long`	`timeOutInterval` Time after which the executing script would be timedout
`static String`	`ULIMIT_COMMAND` a Unix command to get ulimit of a process.
`static 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 and Description

Shell()

Shell(long interval)

Constructors
Constructor and Description
`Shell()`
`Shell(long interval)`

Method Summary

All Methods Static Methods Instance Methods Abstract Methods Concrete Methods
Modifier and Type	Method and Description
`static String`	`execCommand(Map<String,String> env, String... cmd)` Static method to execute a shell command.
`static String`	`execCommand(Map<String,String> env, String[] cmd, long timeout)` Static method to execute a shell command.
`static String`	`execCommand(String... cmd)` Static method to execute a shell command.
`protected abstract String[]`	`getExecString()` return an array containing the command name and its parameters
`int`	`getExitCode()` get the exit code
`static String[]`	`getGET_PERMISSION_COMMAND()` Return a Unix command to get permission information.
`static String[]`	`getGroupsCommand()` a Unix command to get the current user's groups list
`static String[]`	`getGroupsForUserCommand(String user)` a Unix command to get a given user's groups list
`Process`	`getProcess()` get the current sub-process executing the given command
`static 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(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(Map<String,String> env)` set the environment for the command
`protected void`	`setWorkingDirectory(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 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 String SET_PERMISSION_COMMAND
```
    a Unix command to set permission
    
    See Also:
    
    Constant Field Values
  - SET_OWNER_COMMAND
```
public static final String SET_OWNER_COMMAND
```
    a Unix command to set owner
    
    See Also:
    
    Constant Field Values
  - SET_GROUP_COMMAND
```
public static final 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 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 String[] getGroupsCommand()
```
    a Unix command to get the current user's groups list
  - getGroupsForUserCommand
```
public static String[] getGroupsForUserCommand(String user)
```
    a Unix command to get a given user's groups list
  - getGET_PERMISSION_COMMAND
```
public static String[] getGET_PERMISSION_COMMAND()
```
    Return a Unix command to get permission information.
  - getUlimitMemoryCommand
```
public static 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(Map<String,String> env)
```
    set the environment for the command
    
    Parameters:
    
    env - Mapping of environment variables
  - setWorkingDirectory
```
protected void setWorkingDirectory(File dir)
```
    set the working directory
    
    Parameters:
    
    dir - The directory where the command would be executed
  - run
```
protected void run()
            throws IOException
```
    check to see if a command needs to be executed and execute if needed
    
    Throws:
    
    IOException
  - getExecString
```
protected abstract String[] getExecString()
```
    return an array containing the command name and its parameters
  - parseExecResult
```
protected abstract void parseExecResult(BufferedReader lines)
                                 throws IOException
```
    Parse the execution result
    
    Throws:
    
    IOException
  - getProcess
```
public 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 String execCommand(String... cmd)
                          throws 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:
    
    IOException
  - execCommand
```
public static String execCommand(Map<String,String> env,
                                 String[] cmd,
                                 long timeout)
                          throws 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:
    
    IOException
  - execCommand
```
public static String execCommand(Map<String,String> env,
                                 String... cmd)
                          throws 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:
    
    IOException

Class Shell

Nested Class Summary

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

USER_NAME_COMMAND

SET_PERMISSION_COMMAND

SET_OWNER_COMMAND

SET_GROUP_COMMAND

timeOutInterval

ULIMIT_COMMAND

WINDOWS

Constructor Detail

Shell

Shell

Method Detail

getGroupsCommand

getGroupsForUserCommand

getGET_PERMISSION_COMMAND

getUlimitMemoryCommand

setEnvironment

setWorkingDirectory

run

getExecString

parseExecResult

getProcess

getExitCode

isTimedOut

execCommand

execCommand

execCommand