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

Name	Description	Notes
execl, execle, execlp, execlpe	load 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, execvpe	load 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, spawnlpe	load and execute a new child process. Parameters are passed individually.	DOS,Win,OS/2
spawnv, spawnve, spawnvp, spawnvpe	load and execute a new child process. Parameters are passed as an array of pointers.	DOS,Win,OS/2
beginthread, beginthreadNT	creates a new thread of execution within the current process.	Win,OS/2
endthread	terminates a thread created by beginthread.	Win,OS/2
getpid	returns the process identifier.	DOS,Win,OS/2
cexit	restore interrupt vectors altered by the startup code.	DOS,Win,OS/2

Member constants

Name	Description	Notes	OS
_P_WAIT	Suspends parent process until the child process has finished executing.	synchronous spawn.	MS-DOS,Win32,OS/2
_P_NOWAIT, _P_NOWAITO	Continues to execute calling process concurrently with new process.	asynchronous spawn.	Win32,OS/2
_P_OVERLAY	Overlays parent process with child, which destroys the parent.	has the same effect as the exec* functions.	MS-DOS,Win32,OS/2
_P_DETACH	The 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_CHILD	used as cwait action.	Obsolete on Win32.	MS-DOS,OS/2
_WAIT_GRANDCHILD	used 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.

• DJGPP^[3][4]
• OpenWatcom,^[5][6]
• Digital Mars^[7][8]
• MinGW^[9]
• Microsoft Visual C++^[10]
• Borland Turbo C, 2.0 and later^[11][12]
• Lcc32^[13]
• QNX Neutrino QCC 6.x^[14]

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
2. Is my floppy diskette formated?, groups-beta.google.com
3. Delorie.com
4. DJGPP process.h, delorie.com
5. Openwatcom.org
6. OpenWatcom clib, openwatcom.org
7. DigitalMars.com
8. Digital Mars process.h, digitalmars.com
9. MinGW.org
10. MSDN.Microsoft.com
11. Borland.com
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

External links

• Digital Mars _exec reference