fork(2)                                                   fork(2)



     NAME
          fork - create a new process

     SYNOPSIS
          int fork ()

     DESCRIPTION
          fork 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_ING,
             function address)
             set-user-ID mode bit
             set-group-ID mode bit
             profiling on/off status
             access groups (see getgroups(2))
             nice value (see nice(2))
             all attached shared memory segments (see shmop(2))
             process group ID
             tty group ID (see exit(2) and signal(3))
             trace flag (see ptrace(2) request 0)
             time left until an alarm clock signal (see alarm(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 (see times(2)).  The time left until an alarm
             clock signal is reset to 0.



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     fork(2)                                                   fork(2)



          fork will fail and no child process will be created if one
          or more of the following are 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.

     RETURN VALUE
          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 errno is set to indicate the error.

     SEE ALSO
          exec(2), nice(2), plock(2), ptrace(2), semop(2), shmop(2),
          signal(3), times(2).

































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