Sunday, January 20, 2013

POSIX


POSIX for Windows

Cygwin provides a largely POSIX-compliant development and run-time environment for Microsoft Windows.MinGW, formerly a fork of Cygwin, provides less POSIX-compliant development environment and supports compatible C-programmed applications via Msvcrt, Microsoft's old Visual C runtime library.Microsoft POSIX subsystem, an optional Windows subsystem included in Windows NT-based operating systems up to Windows 2000. Partial POSIX-1 — no threads, no sockets.Interix, originally OpenNT by Softway Systems, Inc., is an upgrade and replacement for Microsoft POSIX subsystemthat was purchased by Microsoft in 1999. It was initially marketed as a stand-alone add-on product and then later included it as a component in Windows Services for UNIX(SFU) and finally incorporated it as a component in Windows Vista and later Windows OS releases under the name "Subsystem for UNIX-based Applications" (SUA). It enables full POSIX compliance for certain Microsoft Windows products[citation needed].UWIN from AT&T Research implements a POSIX layer on top of the Win32 APIs.MKS Toolkit, originally created for MS-DOS, is a software package produced and maintained by MKS Inc. that provides a Unix-like environment for scripting, connectivity and porting Unix and Linux software to both 32- and 64-bit Microsoft Windows systems. A demonstration version of this was included in the first release of Windows Services for UNIX (SFU).[citation needed]

POSIX for OS/2

Mostly POSIX compliant environments for OS/2:emx+gcc – largely POSIX compliant

POSIX for DOS

Partially POSIX compliant environments for DOS include:emx+gcc – largely POSIX compliantDJGPP – partially POSIX compliant

Compliant via compatibility feature

The following are not officially certified as POSIX compatible, but they conform in large part to the standards by implementing POSIX support via some sort of compatibility feature, usually translation libraries, or a layer atop the kernel. Without these features, they are usually noncompliant.eCos – POSIX is part of standard distribution, and used by many applications. 'external links' section below has more information.MorphOS (through the built-in ixemul library)OpenVMS (through optional POSIX package)OpenVOS is an optional POSIX-compliant layer atop the Stratus VOS kernel[16]Plan 9 from Bell Labs APE - ANSI/POSIX Environment[17]Symbian OS with PIPS (PIPS Is POSIX on Symbian)Windows NT kernel when using Microsoft SFU 3.5 or SUAWindows 2000 Server or Professional with Service Pack 3 or later. To be POSIX compliant, one must activate optional features of Windows NT and Windows 2000 Server.[18]Windows XP Professional with Service Pack 1 or laterWindows Server 2003Windows VistaWindows 7z/OSClose this section

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POSIX signalPOSIX ThreadsPOSIX sockets are basically Berkeley sockets[citation needed]TRON project – alternative OS standard to POSIXInterix – a full-featured POSIX and Unix environment subsystem for Microsoft's Windows NT-based operating systemsC POSIX libraryReal-time operating systemClose this section


POSIX

Not to be confused with Unix, Unix-like, or Linux.POSIX (pron.: /ˈpɒzɪks/ poz-iks), an acronym for "Portable Operating System Interface", is a family of standards specified by the IEEE for maintaining compatibility between operating systems. POSIX defines the application programming interface (API), along with command line shells and utility interfaces, for software compatibility with variants of Unixand other operating systems.[1][2]

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The POSIX specifications for Unix-like operating systemenvironments originally consisted of a single document for the core programming interface, but eventually grew to 19 separate documents (for example, POSIX.1, POSIX.2 etc.) [1]. The standardized user command line and scripting interface were based on the Korn shell[citation needed]. Many user-level programs, services, and utilities including awk, echo, ed were also standardized, along with required program-level services including basic I/O (file, terminal, andnetwork) services. POSIX also defines a standard threadinglibrary API which is supported by most modern operating systems. Nowadays, most of POSIX parts are combined into a single standard, IEEE Std 1003.1-2008, also known as POSIX.1-2008.As of 2009, POSIX documentation is divided in two parts:POSIX.1-2008: POSIX Base Definitions, System Interfaces, and Commands and Utilities (which include POSIX.1, extensions for POSIX.1, Real-time Services, Threads Interface, Real-time Extensions, Security Interface, Network File Access and Network Process-to-Process Communications, User Portability Extensions, Corrections and Extensions, Protection and Control Utilities and Batch System Utilities)POSIX Conformance Testing: A test suite for POSIX accompanies the standard: PCTS or the POSIX Conformance Test Suite.[3]The development of the POSIX standard takes place in the Austin Group, a joint working group linking the Open Group and the ISO organization.Close this section

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Parts before 1997

Before 1997, POSIX comprised several standards:

POSIX.1

POSIX.1, Core Services (incorporates Standard ANSI C) (IEEE Std 1003.1-1988)Process Creation and ControlSignalsFloating Point ExceptionsSegmentation / Memory ViolationsIllegal InstructionsBus ErrorsTimersFile and Directory OperationsPipesC Library (Standard C)I/O Port Interface and ControlProcess Triggers

POSIX.1b

POSIX.1b, Real-time extensions (IEEE Std 1003.1b-1993)Priority SchedulingReal-Time SignalsClocks and TimersSemaphoresMessage PassingShared MemoryAsynch and Synch I/OMemory Locking Interface

POSIX.1c

POSIX.1c, Threads extensions (IEEE Std 1003.1c-1995)Thread Creation, Control, and CleanupThread SchedulingThread SynchronizationSignal Handling

POSIX.2

POSIX.2, Shell and Utilities (IEEE Std 1003.2-1992)Command InterpreterUtility Programs

Versions after 1997

After 1997, the Austin Group developed the POSIX revisions. The specifications are known under the name Single UNIX Specification, before they become a POSIX standard when formally approved by the ISO.

POSIX.1-2001

POSIX.1-2001 or IEEE Std 1003.1-2001 equates to the Single UNIX Specification version 3[4]This standard consisted of:the Base Definitions, Issue 6,the System Interfaces and Headers, Issue 6,the Commands and Utilities, Issue 6.

POSIX.1-2001 (with two TCs)

IEEE Std 1003.1-2004 involved a minor update of POSIX.1-2001. It incorporated two technical corrigenda.[5] Its contents are available on the web.[6]

POSIX.1-2008

As of 2009POSIX.1-2008 or IEEE Std 1003.1-2008 represents the current version.[7][8] A free online copy is available.[9]This standard consists of:the Base Definitions, Issue 7,the System Interfaces and Headers, Issue 7,the Commands and Utilities, Issue 7.Close this section

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512- vs 1024-byte blocks

POSIX mandates 512-byte block sizes for the df and duutilities, reflecting the default size of blocks on disks. When Richard Stallman and the GNU team were implementing POSIX for the GNU operating system, they objected to this on the grounds that most people think in terms of 1024 byte (or 1 KiB) blocks. The environmental variable POSIXLY_CORRECT was introduced to force the standards-compliant behaviour.[10] The variable POSIX_ME_HARDERwas also discussed[11] and was implemented in a few packages[citation needed] before being obsoleted by POSIXLY_CORRECT.Close this section

HidePOSIX-oriented operating systems

Depending upon the degree of compliance with the standards, one can classify operating systems as fully or partly POSIX compatible. Certified products can be found at the IEEE's website.[12]

Fully POSIX-compliant

The following operating systems conform (i.e., are 100% compliant) to one or more of the various POSIX standards.A/UXAIXBSD/OSDSPnanoHP-UXINTEGRITYIRIXLynxOSMPE/iXOS X[13]QNX[14]RTEMS(POSIX 1003.13-2003 Profile 52)SolarisTru64Unison RTOSUnixWare

Mostly POSIX-compliant

This section requires expansion. (January 2007)The following, while not officially certified as POSIX compatible, conform in large part:BeOS / HaikuFreeBSD[15]GNU/Linux (most distributions — see Linux Standard Base)ContikiillumosMINIXNetBSDNucleus RTOSOpenBSDOpenSolarisPikeOS RTOS for embedded systems with optional PSE51 and PSE52 partitions; see partition (mainframe)RTEMS – POSIX API support designed to IEEE Std. 1003.13-2003 PSE52SanosSkyOSSyllableVSTaVxWorks[14] ( VxWorks is often used as a shell around non-posix Kernels i.e. TiMOS/SROS )

POSIX for Windows

Cygwin provides a largely POSIX-compliant development and run-time environment for Microsoft Windows.MinGW, formerly a fork of Cygwin, provides less POSIX-compliant development environment and supports compatible C-programmed applications via Msvcrt, Microsoft's old Visual C runtime library.Microsoft POSIX subsystem, an optional Windows subsystem included in Windows NT-based operating systems up to Windows 2000. Partial POSIX-1 — no threads, no sockets.Interix, originally O


.  /proc/mdstat

This file contains the current information for multiple-disk, RAID configurations. If the system does not contain such a configuration, then /proc/mdstat looks similar to the following:Personalities : read_ahead not set unused devices: <none>This file remains in the same state as seen above unless a software RAID or md device is present. In that case, view /proc/mdstat to find the current status of mdX  RAID devices.The /proc/mdstat file below shows a system with its md0 configured as a RAID 1 device, while it is currently re-syncing the disks:Personalities : [linear] [raid1] read_ahead 1024 sectors md0: active raid1 sda2[1] sdb2[0] 9940 blocks [2/2] [UU] resync=1% finish=12.3min algorithm 2 [3/3] [UUU] unused devices: <none>


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