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OpenDarwin 7.2.1 - man page for fork (opendarwin section 2)

FORK(2) 			     BSD System Calls Manual				  FORK(2)

NAME
     fork -- create a new process

SYNOPSIS
     #include <sys/types.h>
     #include <unistd.h>

     pid_t
     fork(void);

DESCRIPTION
     Fork() causes creation of a new process.  The new process (child process) is an exact copy
     of the calling process (parent process) except for the following:

	   o   The child process has a unique process ID.

	   o   The child process has a different parent process ID (i.e., the process ID of the
	       parent process).

	   o   The child process has its own copy of the parent's descriptors.	These descriptors
	       reference the same underlying objects, so that, for instance, file pointers in
	       file objects are shared between the child and the parent, so that an lseek(2) on a
	       descriptor in the child process can affect a subsequent read or write by the par-
	       ent.  This descriptor copying is also used by the shell to establish standard
	       input and output for newly created processes as well as to set up pipes.

	   o   The child processes resource utilizations are set to 0; see setrlimit(2).

RETURN VALUES
     Upon successful completion, fork() returns a value of 0 to the child process and returns the
     process ID of the child process to the parent process.  Otherwise, a value of -1 is returned
     to the parent process, no child process is created, and the global variable errno is set to
     indicate the error.

ERRORS
     Fork() will fail and no child process will be created if:

     [EAGAIN]		The system-imposed limit on the total number of processes under execution
			would be exceeded.  This limit is configuration-dependent.

     [EAGAIN]		The system-imposed limit MAXUPRC (<sys/param.h>) on the total number of
			processes under execution by a single user would be exceeded.

     [ENOMEM]		There is insufficient swap space for the new process.

SEE ALSO
     execve(2), wait(2)

HISTORY
     A fork() function call appeared in Version 6 AT&T UNIX.

4th Berkeley Distribution		   June 4, 1993 		4th Berkeley Distribution


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