fork(2)                                                             fork(2)


   NAME
         fork - create a new process

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

         pidt fork(void);

   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:

               real user ID, real group ID, effective user ID, effective group
               ID
               environment
               close-on-exec flag [see exec(2)]
               signal handling settings (i.e., SIGDFL, SIGIGN, SIGHOLD,
               function address)
               supplementary group IDs
               set-user-ID mode bit
               set-group-ID mode bit
               profiling on/off status
               nice value [see nice(2)]
               scheduler class [see priocntl(2)]
               all attached shared memory segments [see shmop(2)]
               process group ID
               session ID [see exit(2)]
               current working directory
               root directory
               file mode creation mask [see umask(2)]
               resource limits [see getrlimit(2)]
               controlling terminal

         Scheduling priority and any per-process scheduling parameters that
         are specific to a given scheduling class may or may not be inherited
         according to the policy of that particular class [see priocntl(2)].

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

               The child process has a unique process ID which does not match
               any active process group ID.

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





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   fork(2)                                                             fork(2)


               The child process has its own copy of the parent's file
               descriptors and directory streams.  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 tms structure is cleared:  tmsutime,
               stime, cutime, and cstime are set to 0 [see times(2)].

               The time left until an alarm clock signal is reset to 0.

               The set of signals pending for the child process is initialized
               to the empty set.

         Record locks set by the parent process are not inherited by the child
         process [see fcntl(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 by a single user would be
                        exceeded.

         EAGAIN         Total amount of system memory available when reading
                        via raw I/O is temporarily insufficient.

         ENOMEM         There is not enough swap space.

   SEE ALSO
         alarm(2), exec(2), fcntl(2), getrlimit(2), nice(2), plock(2),
         priocntl(2), ptrace(2), semop(2), shmop(2), signal(2), times(2),
         umask(2), wait(2), system(3S).

   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 (pidt)-1 is returned to the parent
         process, no child process is created, and errno is set to indicate
         the error.









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