CLONE(2) BSD System Calls Manual CLONE(2)
clone, __clone -- spawn new process with options
Standard C Library (libc, -lc)
clone(int (*func)(void *arg), void *stack, int flags, void *arg);
__clone(int (*func)(void *arg), void *stack, int flags, void *arg);
The clone system call (and associated library support code) creates a new process in a way that allows the caller to specify several options
for the new process creation.
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 direc-
tion 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
CLONE_VM Share the virtual address space with the parent. The address space is shared in the same way as vfork(2).
CLONE_FS Share the ``file system information'' with the parent. This include the current working directory and file creation mask.
CLONE_FILES Share the file descriptor table with the parent.
CLONE_SIGHAND Share the signal handler set with the parent. Note that the signal mask is never shared between the parent and the child,
even if CLONE_SIGHAND is set.
CLONE_VFORK Preserve the synchronization semantics of vfork(2); the parent blocks until the child exits.
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
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.
Same as for fork(2).
Same as for fork(2).
chdir(2), chroot(2), fork(2), sigaction(2), sigprocmask(2), umask(2), vfork(2), wait(2)
The clone() function call appeared in NetBSD 1.6. It is compatible with the Linux function call of the same name with respect to the
The NetBSD implementation of clone() does not implement the following flags that are present in the Linux implementation:
May 4, 2010 BSD