OS (OpenHFT/Chronicle Core 2.27ea0 API)

java.lang.Object
- net.openhft.chronicle.core.OS

```
public final class OS
extends Object
```
Low level access to OS class. The OS class provides utility methods related to the operating system.

Field Summary

Fields
Modifier and Type Field and Description

static int SAFE_PAGE_SIZE

static Exception TIME_LIMIT

static String TMP

static String USER_HOME

Fields
Modifier and Type	Field and Description
`static int`	`SAFE_PAGE_SIZE`
`static Exception`	`TIME_LIMIT`
`static String`	`TMP`
`static String`	`USER_HOME`

Method Summary

All Methods Static Methods Concrete Methods
Modifier and Type	Method and Description
`static int`	`defaultOsPageSize()` Returns default OS page size.
`static @NotNull String`	`findDir(@NotNull String suffix)` Finds a directory with the specified suffix in the class path.
`static @NotNull File`	`findFile(String... path)` Search a list of directories to find a path which is the last element.
`static String`	`getHostName()` Returns the host name of the current machine.
`static String`	`getIPAddress()` Returns the IP address of the current machine.
`static long`	`getPidMax()`
`static int`	`getProcessId()` Returns the process ID of the current running process.
`static String`	`getTarget()` Returns the target of the operating system.
`static String`	`getTmp()` Returns the temporary directory path.
`static String`	`getUserDir()`
`static String`	`getUserName()` Returns the username of the current user.
`static boolean`	`is64Bit()`
`static boolean`	`isLinux()` Returns if this JVM runs on the Linux operating system.
`static boolean`	`isMacOSX()` Returns if this JVM runs on the MacOS operating system.
`static boolean`	`isSparseFileSupported()` Checks if the operating system supports sparse files
`static boolean`	`isWindows()` Returns if this JVM runs on the Windows operating system.
`static long`	`map(@NotNull FileChannel fileChannel, FileChannel.MapMode mode, long start, long size)`
`static long`	`map(@NotNull FileChannel fileChannel, FileChannel.MapMode mode, long start, long size, int pageSize)` Map a region of a file into memory.
`static long`	`mapAlign(long offset)` Aligns the specified offset for a memory-mapped file based on the operating system's page size.
`static long`	`mapAlign(long offset, int pageAlignment)` Aligns the specified offset for a memory-mapped file to the nearest higher multiple of the given pageAlignment.
`static long`	`mapAlignment()` Returns the alignment of offsets in file, from which memory mapping could start, based on OS.
`static @NotNull Memory`	`memory()`
`static long`	`memoryMapped()` Returns the number of bytes that is memory mapped.
`static long`	`pageAlign(long size)` Align the size to page boundary
`static long`	`pageAlign(long size, int pageSize)` Align the size to page boundary
`static int`	`pageSize()`
`static int`	`read0(FileDescriptor fd, long address, int len)`
`static long`	`spaceUsed(@NotNull String filename)` Get the space actually used by a file.
`static void`	`unmap(long address, long size)`
`static void`	`unmap(long address, long size, int pageSize)` Unmap a region of memory.
`static String`	`userDir()` Returns the current working directory of the user.
`static int`	`write0(FileDescriptor fd, long address, int len)`

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

- Field Detail
  - USER_HOME
```
public static final String USER_HOME
```
  - TIME_LIMIT
```
public static final Exception TIME_LIMIT
```
  - SAFE_PAGE_SIZE
```
public static final int SAFE_PAGE_SIZE
```
    See Also:
    
    Constant Field Values
  - TMP
```
public static final String TMP
```
- Method Detail
  - isSparseFileSupported
```
public static boolean isSparseFileSupported()
```
    Checks if the operating system supports sparse files
    
    Returns:
    
    if the OS supports sparse files
  - findDir
```
@NotNull
public static @NotNull String findDir(@NotNull
                                               @NotNull String suffix)
                                        throws FileNotFoundException
```
    Finds a directory with the specified suffix in the class path.
    
    Parameters:
    
    suffix - the suffix of the directory
    
    Returns:
    
    the path of the found directory
    
    Throws:
    
    FileNotFoundException - if no directory with the specified suffix is found
  - findFile
```
@NotNull
public static @NotNull File findFile(@NotNull
                                              String... path)
```
    Search a list of directories to find a path which is the last element.
    
    Parameters:
    
    path - of directories to use if found, the last path is always appended.
    
    Returns:
    
    the resulting File path.
  - getHostName
```
public static String getHostName()
```
    Returns the host name of the current machine.
    
    Returns:
    
    the host name
  - getIPAddress
```
public static String getIPAddress()
```
    Returns the IP address of the current machine.
    
    Returns:
    
    the IP address
  - getUserName
```
public static String getUserName()
```
    Returns the username of the current user.
    
    Returns:
    
    the username
  - getTarget
```
public static String getTarget()
```
    Returns the target of the operating system.
    
    Returns:
    
    the target
  - getTmp
```
public static String getTmp()
```
    Returns the temporary directory path.
    
    Returns:
    
    the temporary directory path
  - getUserDir
```
public static String getUserDir()
```
    Returns:
    
    the current working directory
  - memory
```
@NotNull
public static @NotNull Memory memory()
```
    Returns:
    
    native memory accessor class
  - pageAlign
```
public static long pageAlign(long size,
                             int pageSize)
```
    Align the size to page boundary
    
    Parameters:
    
    size - the size to align
    
    pageSize - the size of pages
    
    Returns:
    
    aligned size
    
    See Also:
    
    pageSize()
  - pageAlign
```
public static long pageAlign(long size)
```
    Align the size to page boundary
    
    Parameters:
    
    size - the size to align
    
    Returns:
    
    aligned size
    
    See Also:
    
    pageSize()
  - pageSize
```
public static int pageSize()
```
    Returns:
    
    size of pages
    
    See Also:
    
    pageAlign(long)
  - defaultOsPageSize
```
public static int defaultOsPageSize()
```
    Returns default OS page size.
  - mapAlign
```
public static long mapAlign(long offset)
```
    Aligns the specified offset for a memory-mapped file based on the operating system's page size. Memory mapping typically requires that the offset be aligned to the operating system's page size. This method calculates the nearest higher offset that meets this alignment requirement.
    For example, if the operating system's page size is 4096 bytes and an offset of 6000 is specified, this method would return 8192, as 8192 is the next multiple of 4096 greater than 6000.
    
    Parameters:
    
    offset - the offset to be aligned. It must be non-negative.
    
    Returns:
    
    the aligned offset.
    
    Throws:
    
    IllegalArgumentException - if offset is negative.
    
    See Also:
    
    mapAlignment()
  - mapAlign
```
public static long mapAlign(long offset,
                            int pageAlignment)
```
    Aligns the specified offset for a memory-mapped file to the nearest higher multiple of the given pageAlignment. This method calculates the nearest higher offset that meets this alignment requirement.
    For example, if the provided alignment is 2M bytes and an offset of 2.5M is specified, this method would return 4M, as 4M is the next multiple of 2M greater than 2.5M.
    
    Parameters:
    
    offset - the offset to be aligned. It must be non-negative.
    
    pageAlignment - the alignment size, in bytes. This should typically be the operating system's page size or a multiple thereof.
    
    Returns:
    
    the aligned offset.
    
    Throws:
    
    IllegalArgumentException - if offset is negative or pageAlignment is non-positive.
  - mapAlignment
```
public static long mapAlignment()
```
    Returns the alignment of offsets in file, from which memory mapping could start, based on OS.
    
    Returns:
    
    granularity of an offset in a file
    
    See Also:
    
    mapAlign(long)
  - is64Bit
```
public static boolean is64Bit()
```
    Returns:
    
    is the JVM 64-bit
  - getProcessId
```
public static int getProcessId()
```
    Returns the process ID of the current running process.
    Note: Getting the process ID may be slow if the reserve DNS is not set up correctly.
    
    Returns:
    
    the process ID
  - isWindows
```
public static boolean isWindows()
```
    Returns if this JVM runs on the Windows operating system.
    
    Returns:
    
    if runs on Windows
  - isMacOSX
```
public static boolean isMacOSX()
```
    Returns if this JVM runs on the MacOS operating system.
    
    Returns:
    
    if runs on MacOS
  - isLinux
```
public static boolean isLinux()
```
    Returns if this JVM runs on the Linux operating system.
    
    Returns:
    
    if runs on Linux
  - getPidMax
```
public static long getPidMax()
```
    Returns:
    
    the maximum PID.
  - map
```
public static long map(@NotNull
                       @NotNull FileChannel fileChannel,
                       FileChannel.MapMode mode,
                       long start,
                       long size,
                       int pageSize)
                throws IOException,
                       IllegalArgumentException
```
    Map a region of a file into memory.
    
    Parameters:
    
    fileChannel - to map
    
    mode - of access
    
    start - offset within a file
    
    size - of region to map.
    
    Returns:
    
    the address of the memory mapping.
    
    Throws:
    
    IOException - if the mapping fails
    
    IllegalArgumentException - if the arguments are not valid
  - map
```
public static long map(@NotNull
                       @NotNull FileChannel fileChannel,
                       FileChannel.MapMode mode,
                       long start,
                       long size)
                throws IOException,
                       IllegalArgumentException
```
    Throws:
    
    IOException
    
    IllegalArgumentException
  - unmap
```
public static void unmap(long address,
                         long size,
                         int pageSize)
                  throws IOException
```
    Unmap a region of memory.
    
    Parameters:
    
    address - of the start of the mapping.
    
    size - of the region mapped.
    
    Throws:
    
    IOException - if the unmap fails.
  - unmap
```
public static void unmap(long address,
                         long size)
                  throws IOException
```
    Throws:
    
    IOException
  - memoryMapped
```
public static long memoryMapped()
```
    Returns the number of bytes that is memory mapped.
    
    Returns:
    
    bytes memory mapped
  - spaceUsed
```
public static long spaceUsed(@NotNull
                             @NotNull String filename)
```
    Get the space actually used by a file.
    
    Parameters:
    
    filename - to get the actual size of
    
    Returns:
    
    size in bytes.
  - userDir
```
public static String userDir()
```
    Returns the current working directory of the user.
    
    Returns:
    
    the user's current working directory
  - read0
```
public static int read0(FileDescriptor fd,
                        long address,
                        int len)
                 throws IOException
```
    Throws:
    
    IOException
  - write0
```
public static int write0(FileDescriptor fd,
                         long address,
                         int len)
                  throws IOException
```
    Throws:
    
    IOException

Class OS

Field Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

USER_HOME

TIME_LIMIT

SAFE_PAGE_SIZE

TMP

Method Detail

isSparseFileSupported

findDir

findFile

getHostName

getIPAddress

getUserName

getTarget

getTmp

getUserDir

memory

pageAlign

pageAlign

pageSize

defaultOsPageSize

mapAlign

mapAlign

mapAlignment

is64Bit

getProcessId

isWindows

isMacOSX

isLinux

getPidMax

map

map

unmap

unmap

memoryMapped

spaceUsed

userDir

read0

write0