| CLONE(2) | System Calls Manual | CLONE(2) | 
clone, __clone —
#define _GNU_SOURCE
#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_VMCLONE_FSCLONE_FILESCLONE_SIGHANDCLONE_SIGHAND is set.CLONE_VFORKThe 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:
| August 1, 2022 | NetBSD 10.0 |