FORK(2-SVR3)        RISC/os Reference Manual         FORK(2-SVR3)



NAME
     fork - create a new process

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

     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_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 inher-
          ited 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.




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FORK(2-SVR3)        RISC/os Reference Manual         FORK(2-SVR3)



ERRORS
     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.

     [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 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.


























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