fork(2)                                                         fork(2)

  fork()

  NAME

    fork() - create a new process

  SYNOPSIS

    #include 

    pid_t fork (void)

  DESCRIPTION

    The fork(2) function causes creation of a new process. The new process
    (child process) is an exact copy of the calling process (parent 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(2) or write(2) 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 process's values of tms_utime tms_stime tms_cutime and
          tms_cstime are set to zero.
    *     The child does not inherit any file locks set by the parent.
    *     Any pending alarms have been cleared for the child process.
    *     Signals pending for the child process have been initialized to the
          empty set.

  RETURN VALUES

    Upon successful completion, fork(2) 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 the global variable errno is set to indicate
    the error.

  ERRORS

    The fork(2) function will fail and no child process will be created if:

    [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 on the total number of processes under
        execution by a single user would be exceeded.

    [ENOMEM]
        Insufficient memory is available.

  SEE ALSO

    exec(2)

    vfork(2)

    wait(2)

  USAGE NOTES

    The fork function is thread safe.

    The fork function is async-signal safe.