CLONE(2) | System Calls Manual | CLONE(2) |
clone
, __clone
—
#include <sched.h>
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);
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 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.
clone
() function call appeared in
NetBSD 1.6. It is compatible with the Linux function
call of the same name with respect to the described options.
clone
() does not implement the following
flags that are present in the Linux implementation:
May 4, 2010 | NetBSD 9.0 |