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FORK(2) 		       System Calls Manual			 FORK(2)

NAME
     fork -- create a new process

LIBRARY
     Standard C Library (libc, -lc)

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

     pid_t
     fork(void);

DESCRIPTION
     The  fork()  system call 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:

	   *   The child process has a unique process ID.

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

	   *   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.

	   *   The  child process' resource utilizations are set to 0; see setr-
	       limit(2).

	   *   All interval timers are cleared; see setitimer(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
     The fork() system call 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 ten 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	argument
			RLIMIT_NPROC would be exceeded (see getrlimit(2)).

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

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

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

FreeBSD 8.1			  June 4, 1993				 FORK(2)
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