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. 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.

External links

• Digital Mars _exec reference