process.h

process.h is a 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.

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.

Member 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

Member 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.

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]
gollark: I suppose you could argue that it isn't really relevant, since it can't run in the actual universe.
gollark: It also can't model itself.
gollark: It's an (uncomputable) algorithm which is boundedly worse than the best (computable) algorithm to infer things and it's arguably general intelligence.
gollark: Well, we have Solomonoff induction.
gollark: By which I mean subjective experience/whatever causes humans to talk about being conscious all the time, not planning ability and such.

References
  1. "Copyright 1985–1989, Microsoft Corporation", in QuickC version 2.00 process.h file
  2. Is my floppy diskette formated?, groups-beta.google.com
  3. Delorie.com
  4. DJGPP process.h, delorie.com
  5. Openwatcom.org Archived 2015-03-17 at the Wayback Machine
  6. OpenWatcom clib Archived 2006-10-11 at the Wayback Machine, openwatcom.org
  7. DigitalMars.com
  8. Digital Mars process.h, digitalmars.com
  9. MinGW.org
  10. "MSDN.Microsoft.com". Archived from the original on 2007-07-07. Retrieved 2007-01-15.
  11. "Borland.com". Archived from the original on 2012-11-05. Retrieved 2007-01-15.
  12. C version 2.01, dn.codegear.com
  13. CS.Virginia.edu
  14. QNX.com
  15. DJGPP spawn*, delorie.com
  16. Microsoft MSDN, msdn.microsoft.com
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