Pexec() has many functions designed to spawn child processes depending on the selected mode.

75 (0x4B)

Pexec() modes 0, 3, 4, and 5, are available in all GEMDOS versions. Mode 6 is available as of GEMDOS version 0.15. Mode 6 is available as of GEMDOS version 0.19. Modes 100, 104, 106, and 200 are only available in the presence of MiNT.

mode defines the function of Pexec() and the meaning of its parameters and return value as defined below. For modes which load a program, fname specifies the GEMDOS file specification of the file to load. cmdline is pointer to a string containg the command line which will be passed to the calling program. The first byte of the string should indicate the length of the command line (maximum of 125 bytes). The actual command line starts at byte 2. envstr is a pointer to an environment which is copied and assigned to the child process. If envstr is NULL, the child inherits a copy of the parent's environment.

Name	mode	Meaning
PE_LOADGO	0	'LOAD AND GO' - Load and execute named program file and return a WORD exit code when the child terminates.
PE_LOAD	3	'LOAD, DON'T GO' - Load named program. If successful, the LONG return value is the starting address of the child processes' basepage. The parent owns the memory of the child's environment and basepage and must therefore free them when completed with the child.
PE_GO	4	'JUST GO' - Execute process with basepage at specified address. With this mode, fname and envstr are NULL. The starting address of the basepage of the process to execute is given in the cmdline parameter.
PE_BASEPAGE	5	'CREATE BASEPAGE' - This mode allocates the largest block of free memory and creates a BASEPAGE in the first 256 bytes of it. fname should be set to NULL. It is the responsibility of the parent to load or define the child's code, shrink the memory block as necessary, and initialize the basepage pointers to the TEXT, DATA, and BSS segments of the program. With MiNT, use of this mode in conjunction with mode PE_CGO (104) can be used to emulate the Pvfork()? call without blocking the parent.
PE_GOTHENFREE	6	'JUST GO, THEN FREE' - This mode is identical to mode PE_GO (4) except that memory ownership of the child's environment and basepage belong to the child rather than the parent so that when the child Pterm()'s, that memory is automatically freed.
PE_CLOADGO	100	'LOAD, GO, DON'T WAIT' - This mode is identical to mode PE_LOADGO (0) except that the parent process is returned to immediately while the child continues to execute. The positive process ID of the child is returned. Environment and basepage memory blocks are freed automatically when the child Pterm()'s
PE_CGO	104	'JUST GO, DON'T WAIT' - This mode is similar to mode PE_GO (4) except that the parent process is returned to immediately while the child continues to execute concurrently. The positive process ID of the child is returned. Memory ownership of the environment and basepage are shared by the parent and child (this sharing extends to all memory owned by the parent). fname may be used to supply a name for the child, otherwise, if NULL is used, the name of the parent will be used. cmdline should point to the process basepage. envstr should be NULL.
PE_NOSHARE	106	'JUST GO, DON'T WAIT, NO SHARING' - This mode is exactly the same as mode PE_CGO (104) except that the child process owns its own environment and basepage sharing no memory with the parent.
PE_REPLACE	200	'REPLACE PROGRAM AND GO' - This mode works like mode PE_CLOADGO (100) except that the parent process is terminated immediately and the child process completely replaces the parent in memory retaining the same process ID. fname, cmdline, and envstr, are all normally passed and valid.

	pea	envstr
	pea	cmdline
	pea	fname
	move.w	mode,-(sp)
	move.w	#$4B,-(sp)
	trap	#1
	lea	16(sp),sp

The value returned by Pexec() is dependent on the mode value and is therefore explained above. All Pexec() modes return a LONG negative GEMDOS error code when the call fails. A WORD negative value indicates the child was successfully run but it terminated returning a negative error code. In all cases, a process returning after having been interrupted with Control-C returns 0x0000FFE0 (-32).

Command lines longer than 126 bytes may be passed to processes aware of the AtariExtendedCommandLineSpecification?.