DiskChecker (Hadoop 1.2.1 API)
Date: 2013-07-22

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## org.apache.hadoop.util
Class DiskChecker

    java.lang.Object
      org.apache.hadoop.util.DiskChecker

    public class DiskChecker

extends Object

Class that provides utility functions for checking disk problem

Nested Class Summary
`static class` | `DiskChecker.DiskErrorException`
`static class` | `DiskChecker.DiskOutOfSpaceException`

Constructor Summary
`DiskChecker()`

Method Summary
`static void` | `checkDir(File dir)` Create the directory if it doesn't exist and
`static void` | `checkDir(LocalFileSystem localFS, Path dir, FsPermission expected)` Create the local directory if necessary, check permissions and also ensure it can be read from and written into.
`static boolean` | `mkdirsWithExistsAndPermissionCheck(LocalFileSystem localFS, Path dir, FsPermission expected)` Create the directory or check permissions if it already exists.
`static boolean` | `mkdirsWithExistsCheck(File dir)` The semantics of mkdirsWithExistsCheck method is different from the mkdirs method provided in the Sun's java.io.File class in the following way: While creating the non-existent parent directories, this method checks for the existence of those directories if the mkdir fails at any point (since that directory might have just been created by some other process).

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### DiskChecker

    public DiskChecker()

Method Detail

### mkdirsWithExistsCheck

    public static boolean mkdirsWithExistsCheck(File dir)

  The semantics of mkdirsWithExistsCheck method is different from the mkdirs method provided in the Sun's java.io.File class in the following way: While creating the non-existent parent directories, this method checks for the existence of those directories if the mkdir fails at any point (since that directory might have just been created by some other process). If both mkdir() and the exists() check fails for any seemingly non-existent directory, then we signal an error; Sun's mkdir would signal an error (return false) if a directory it is attempting to create already exists or the mkdir fails.

  Parameters:
    `dir` -
  Returns:
    true on success, false on failure

### checkDir

    public static void checkDir(File dir)
                         throws DiskChecker.DiskErrorException

  Create the directory if it doesn't exist and

  Parameters:
    `dir` -
  Throws:
    `DiskChecker.DiskErrorException`

### mkdirsWithExistsAndPermissionCheck

    public static boolean mkdirsWithExistsAndPermissionCheck(LocalFileSystem localFS,
                                                             Path dir,
                                                             FsPermission expected)
                                                      throws IOException

  Create the directory or check permissions if it already exists. The semantics of mkdirsWithExistsAndPermissionCheck method is different from the mkdirs method provided in the Sun's java.io.File class in the following way: While creating the non-existent parent directories, this method checks for the existence of those directories if the mkdir fails at any point (since that directory might have just been created by some other process). If both mkdir() and the exists() check fails for any seemingly non-existent directory, then we signal an error; Sun's mkdir would signal an error (return false) if a directory it is attempting to create already exists or the mkdir fails.

  Parameters:
    `localFS` - local filesystem
    `dir` - directory to be created or checked
    `expected` - expected permission
  Returns:
    true on success, false on failure
  Throws:
    `IOException`

### checkDir

    public static void checkDir(LocalFileSystem localFS,
                                Path dir,
                                FsPermission expected)
                         throws DiskChecker.DiskErrorException,
                                IOException

  Create the local directory if necessary, check permissions and also ensure it can be read from and written into.

  Parameters:
    `localFS` - local filesystem
    `dir` - directory
    `expected` - permission
  Throws:
    `DiskChecker.DiskErrorException`
    `IOException`

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