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process.h
Non-standard C header file provided by most C compilers targeting MS-DOS, Windows 3.1x, Win32, OS/2 or Novell NetWare

process.h is the C header file which contains function declarations and macros used in working with threads and processes. Most C compilers that target DOS, Windows 3.1x, Win32, OS/2, Novell NetWare or DOS extenders supply this header and the library functions in their C library. Neither the header file nor most of the functions are defined by either the ANSI/ISO C standard or by POSIX.

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History

Microsoft's version of the file dates back to at least 1985, according to its copyright statement.1 An early reference to the file was in a post on the net.micro.pc usenet on Oct-26-1986.2 The compiler used was Microsoft C compiler version 3.0. The Lattice C compiler version 3.30 (Aug-24-1988) did not have such a header file, but offered similar functions. Borland provided the header in their Turbo C compiler version 2.01. The C Ware-Personal C compiler version 1.2c (June 1989) had only the ANSI headers.

Functions

NameDescriptionNotes
execl, execle, execlp, execlpeload and execute a new child process by placing it in memory previously occupied by the parent process. Parameters are passed individually.DOS, Win, OS/2, POSIX
execv, execve, execvp, execvpeload and execute a new child process by placing it in memory previously occupied by the parent process. Parameters are passed as an array of pointers.DOS, Win, OS/2, POSIX
spawnl, spawnle, spawnlp, spawnlpeload and execute a new child process. Parameters are passed individually.DOS, Win, OS/2
spawnv, spawnve, spawnvp, spawnvpeload and execute a new child process. Parameters are passed as an array of pointers.DOS, Win, OS/2
beginthread, beginthreadNTcreates a new thread of execution within the current process.Win, OS/2
endthreadterminates a thread created by beginthread.Win, OS/2
getpidreturns the process identifier.DOS, Win, OS/2
cexitrestore interrupt vectors altered by the startup code.DOS, Win, OS/2

Constants

NameDescriptionNotesOS
_P_WAITSuspends parent process until the child process has finished executing.synchronous spawn.MS-DOS, Win32, OS/2
_P_NOWAIT, _P_NOWAITOContinues to execute calling process concurrently with new process.asynchronous spawn.Win32, OS/2
_P_OVERLAYOverlays parent process with child, which destroys the parent.has the same effect as the exec* functions.MS-DOS, Win32, OS/2
_P_DETACHThe child is run in background without access to the console or keyboard.Calls to _cwait upon the new process will fail. Asynchronous spawn.Win32, OS/2
_WAIT_CHILDused as cwait action.Obsolete on Win32.MS-DOS, OS/2
_WAIT_GRANDCHILDused as cwait action.Obsolete on Win32.MS-DOS, OS/2

Implementations

Given the fact there is no standard on which to base the implementation, the functions declared by process.h differ, depending on the compiler in use. Below is a list of compilers which provide process.h.

  • DJGPP34
  • OpenWatcom,56
  • Digital Mars78
  • MinGW9
  • Microsoft Visual C++10
  • Borland Turbo C, 2.0 and later1112
  • Lcc3213
  • QNX Neutrino QCC 6.x14

Differences

Another aspect that might vary is the combined length of exec* and spawn* parameters.

  • Delorie DJGPP: does not have such a limit.15
  • Digital Mars: the maximum is 128 bytes; nothing is stated about the ending '\0' character.
  • Microsoft cl: the argument list for the new process must not exceed 1024 bytes.16

References

  1. "Copyright 1985–1989, Microsoft Corporation", in QuickC version 2.00 process.h file /wiki/QuickC ↩

  2. Is my floppy diskette formated?[permanent dead link‍], groups-beta.google.com http://groups-beta.google.com/group/net.micro.pc/browse_frm/thread/b85ef1946a4915e6/1154bb52be4d5854?lnk=st&q=%22process%5C.h%22&rnum=23#1154bb52be4d5854 ↩

  3. Delorie.com http://www.delorie.com/djgpp/ ↩

  4. DJGPP process.h, delorie.com http://www.delorie.com/djgpp/doc/incs/process.h ↩

  5. Openwatcom.org Archived 2015-03-17 at the Wayback Machine http://www.openwatcom.org/index.php/Main_Page ↩

  6. OpenWatcom clib Archived 2006-10-11 at the Wayback Machine, openwatcom.org http://www.openwatcom.org/ftp/manuals/clib.pdf ↩

  7. DigitalMars.com http://www.digitalmars.com/ ↩

  8. Digital Mars process.h, digitalmars.com http://www.digitalmars.com/rtl/process.html ↩

  9. MinGW.org http://www.mingw.org/ ↩

  10. "MSDN.Microsoft.com". Archived from the original on 2007-07-07. Retrieved 2007-01-15. https://web.archive.org/web/20070707082306/http://msdn.microsoft.com/vstudio/express/visualc/default.aspx ↩

  11. "Borland.com". Archived from the original on 2012-11-05. Retrieved 2007-01-15. https://web.archive.org/web/20121105211827/http://www.borland.com/ ↩

  12. C version 2.01, dn.codegear.com https://archive.today/20110710191522/http://dn.codegear.com/article/20841Turbo ↩

  13. CS.Virginia.edu http://www.cs.virginia.edu/~lcc-win32/ ↩

  14. QNX.com http://www.qnx.com/products/neutrino_rtos/ ↩

  15. DJGPP spawn*, delorie.com http://www.delorie.com/djgpp/doc/libc/libc_736.html ↩

  16. Microsoft MSDN, msdn.microsoft.com http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vccore98/HTML/_crt_system.2c_._wsystem.asp ↩