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.
History
Microsoft's version of the file dates back to at least 1985, according to its copyright statement. An early reference to the file was in a post on the net.micro.pc usenet on Oct-26-1986. 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
| 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 |
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
- OpenWatcom,
- Digital Mars
- MinGW
- Microsoft Visual C++
- Borland Turbo C, 2.0 and later
- Lcc32
- QNX Neutrino QCC 6.x
Differences
Another aspect that might vary is the combined length of exec* and spawn* parameters.
- Delorie DJGPP: does not have such a limit.
- 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.
References
- "Copyright 1985–1989, Microsoft Corporation", in QuickC version 2.00 process.h file
- Is my floppy diskette formated?, groups-beta.google.com
- Delorie.com
- DJGPP process.h, delorie.com
- Openwatcom.org Archived 2015-03-17 at the Wayback Machine
- OpenWatcom clib Archived 2006-10-11 at the Wayback Machine, openwatcom.org
- DigitalMars.com
- Digital Mars process.h, digitalmars.com
- MinGW.org
- "MSDN.Microsoft.com". Archived from the original on 2007-07-07. Retrieved 2007-01-15.
- "Borland.com". Archived from the original on 2012-11-05. Retrieved 2007-01-15.
- C version 2.01, dn.codegear.com
- CS.Virginia.edu
- QNX.com
- DJGPP spawn*, delorie.com
- Microsoft MSDN, msdn.microsoft.com