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RocketLink!--> Man page versions: OpenBSD FreeBSD NetBSD RedHat Solaris Others

FORK(2)                   OpenBSD Programmer's Manual                  FORK(2)

     fork - create a new process

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


     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

           -   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 de-
               scriptor 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

     Upon successful completion, fork() returns a value of 0 to the child pro-
     cess and returns the process ID of the child process to the parent pro-
     cess.  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.

     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-de-

     [EAGAIN]  The limit RLIMIT_NPROC on the total number of processes under
               execution by the user ID would be exceeded.

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

     execve(2),  setrlimit(2),  wait(2)

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

OpenBSD 2.6                      June 4, 1993                                1

Source: OpenBSD 2.6 man pages. Copyright: Portions are copyrighted by BERKELEY
SOFTWARE DESIGN, INC., The Regents of the University of California, Massachusetts
Institute of Technology, Free Software Foundation, FreeBSD Inc., and others.

(Corrections, notes, and links courtesy of RocketAware.com)

[Detailed Topics]

[Overview Topics]

Up to: Process Creation and Control - child process control (like sending signals), renice, fork, et al

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