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



NAME
     fork - create a new process

SYNOPSIS
     pid = fork()
     int pid;

DESCRIPTION
     fork causes creation of a new process.  The new process
     (child process) is an exact copy of the calling process
     except for the following:

          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
          descriptors.  These descriptors reference the same
          underlying objects, so that, for instance, file
          pointers in file objects are shared between the child
          and the parent, so that an lseek(2) on a descriptor in
          the child process can affect a subsequent read or write
          by the parent.  This descriptor copying is also used by
          the shell to establish standard input and output for
          newly created processes as well as to set up pipes.

          The child processes resource utilizations are set to 0;
          see getrlimit(2).

          The child process does not receive real interval timer
          signals that were arranged by the parent; however, both
          virtual and profiling interval timer signals will con-
          tinue to arrive.

RETURN VALUE
     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 the global variable errno is set to indicate the error.

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.  This
               limit is configuration-dependent.

     [EAGAIN]  The system-imposed limit MAXUPRC (<sys/param.h>)
               on the total number of processes under execution



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



               by a single user would be exceeded.

     [ENOMEM]  There is insufficient swap space for the new pro-
               cess.

SEE ALSO
     execve(2), wait(2).
















































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