fork(2)              INTERACTIVE UNIX System              fork(2)



          NAME
               fork - create a new process

          SYNOPSIS
               int fork ()

          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).  This means the child process
               inherits the following attributes from the parent process:

                    environment
                    close-on-exec flag (see exec(2))
                    signal handling settings (i.e., SIG_DFL, SIG_IGN,
                    SIG_HOLD, function address)
                    set-user-ID mode bit
                    set-group-ID mode bit
                    profiling on/off status
                    nice value (see nice(2))
                    all attached shared memory segments (see shmop(2))
                    process group ID
                    tty group ID (see exit(2))
                    current working directory
                    root directory
                    file mode creation mask (see umask(2))
                    file size limit (see ulimit(2))

               The child process differs from the parent process in the
               following ways:

                    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 file
                    descriptors.  Each of the child's file descriptors
                    shares a common file pointer with the corresponding
                    file descriptor of the parent.

                    All semadj values are cleared (see semop(2)).

                    Process locks, text locks, and data locks are not
                    inherited by the child (see plock(2)).

                    The child process's utime, stime, cutime, and cstime
                    are set to 0.  The time left until an alarm clock sig-
                    nal is reset to 0.

                    Pending alarms are cleared for the child process.

                    The set of signals pending for the child process is


          Rev. 1.2                                                   Page 1

          fork(2)              INTERACTIVE UNIX System              fork(2)



                    initialized to the empty set.

               The fork system call will fail and no child process will be
               created if one or more of the following is true:


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

               [EAGAIN]       The system-imposed limit on the total number
                              of processes under execution by a single user
                              would be exceeded.

               [EAGAIN]       Total amount of system memory available when
                              reading via raw I/O is temporarily insuffi-
                              cient.

               [ENOMEM]       The process requires more space than the sys-
                              tem is able to supply.

          SEE ALSO
               exec(2), nice(2), plock(2), ptrace(2), semop(2), shmop(2),
               signal(2), sigset(2), times(2), ulimit(2), umask(2),
               wait(2).

          DIAGNOSTICS
               Upon successful completion, fork returns a value of 0 to the
               child process and returns the process ID of the child pro-
               cess to the parent process.  Otherwise, a value of -1 is
               returned to the parent process, no child process is created,
               and errno is set to indicate the error.























          Rev. 1.2                                                   Page 2