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., SIGDFL, SIGIGN,
               SIGHOLD, 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
               signal is reset to 0.

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



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     FORK(2)                                                   FORK(2)



          [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 IO is temporarily
                         insufficient.

     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
          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.

     ORIGIN
          AT&T V.3





























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