pid_t
clone(
int (*func)(void *arg)
, void *stack
, int flags
, void *arg
)
pid_t
__clone(
int (*func)(void *arg)
, void *stack
, int flags
, void *arg
)
Unlike fork(2) or vfork(2), in which the child process returns to the call site, clone causes the child process to begin execution at the function specified by func. The argument arg is passed to the entry point, as a means for the parent to provide context to the child. The stack pointer for the child process will be set to stack. Note that the clone interface requires that the application know the stack direction for the architecture, and that the caller initialize the stack argument as appropriate for the stack direction.
The flags argument specifies several options that control how the child process is created. The lower 8 bits of flags specify the signal that is to be sent to the parent when the child exits. The following flags may also be specified by bitwise-or'ing them with the signal value:
CLONE_VM
CLONE_FS
CLONE_FILES
CLONE_SIGHAND
CLONE_SIGHAND
is set.
CLONE_VFORK
The clone call returns the pid of the child in the parent's context. The child is provided no return value, since it begins execution at a different address.
If the child process's entry point returns, the value it returns is passed to _exit(2), and the child process exits. Note that if the child process wants to exit directly, it should use _exit(2), and not exit(3), since exit(3) will flush and close standard I/O channels, and thereby corrupt the parent process's standard I/O data structures (even with fork(2) it is wrong to call exit(3) since buffered data would then be flushed twice).
Note that clone is not intended to be used for new native NetBSD applications. It is provided as a means to port software originally written for the Linux operating system to NetBSD.
)
function call appeared in
NetBSD1.6.
It is compatible with the Linux function call of the same name.
CLONE_PID
option that is present in the Linux implementation.
The
NetBSD
implementation of
clone
does not implement the
CLONE_PTRACE
option that is present in the Linux implementation.