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FORK(2)			  FreeBSD System Calls Manual		       FORK(2)

NAME
     fork -- create a new process

SYNOPSIS
     #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(2)
	       or write(2) by the parent.  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 process' 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 indi-
     cate 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.  The limit is given	by the
	       sysctl(3) MIB variable KERN_MAXPROC.  (The limit	is actually
	       one less	than this except for the super user).

     [EAGAIN]  The user	is not the super user, and the system-imposed limit on
	       the total number	of processes under execution by	a single user
	       would be	exceeded.  The limit is	given by the sysctl(3) MIB
	       variable	KERN_MAXPROCPERUID.

     [EAGAIN]  The user	is not the super user, and the soft resource limit
	       corresponding to	the resource parameter RLIMIT_NPROC would be
	       exceeded	(see getrlimit(2)).

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

SEE ALSO
     execve(2),	rfork(2), setrlimit(2),	vfork(2), wait(2)

HISTORY
     A fork(2) function	call appeared in Version 6 AT&T	UNIX.

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

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUES | ERRORS | SEE ALSO | HISTORY

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