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PDFORK(2)                 FreeBSD System Calls Manual                PDFORK(2)

     pdfork, pdgetpid, pdkill, pdwait4 - System calls to manage process

     Standard C Library (libc, -lc)

     #include <sys/procdesc.h>

     pdfork(int *fdp, int flags);

     pdgetpid(int fd, pid_t *pidp);

     pdkill(int fd, int signum);

     pdwait4(int fd, int *status, int options, struct rusage *rusage);

     Process descriptors are special file descriptors that represent
     processes, and are created using pdfork(), a variant of fork(2), which,
     if successful, returns a process descriptor in the integer pointed to by
     fdp.  Processes created via pdfork() will not cause SIGCHLD on
     termination.  pdfork() can accept the flags:

     PD_DAEMON      Instead of the default terminate-on-close behaviour, allow
                    the process to live until it is explicitly killed with

                    This option is not permitted in capsicum(4) capability
                    mode (see cap_enter(2)).

     PD_CLOEXEC     Set close-on-exec on process descriptor.

     pdgetpid() queries the process ID (PID) in the process descriptor fd.

     pdkill() is functionally identical to kill(2), except that it accepts a
     process descriptor, fd, rather than a PID.

     pdwait4() behaves identically to wait4(2), but operates with respect to a
     process descriptor argument rather than a PID.

     The following system calls also have effects specific to process

     fstat(2) queries status of a process descriptor; currently only the
     st_mode, st_birthtime, st_atime, st_ctime and st_mtime fields are
     defined.  If the owner read, write, and execute bits are set then the
     process represented by the process descriptor is still alive.

     poll(2) and select(2) allow waiting for process state transitions;
     currently only POLLHUP is defined, and will be raised when the process
     dies.  Process state transitions can also be monitored using kqueue(2)
     filter EVFILT_PROCDESC; currently only NOTE_EXIT is implemented.

     close(2) will close the process descriptor unless PD_DAEMON is set; if
     the process is still alive and this is the last reference to the process
     descriptor, the process will be terminated with the signal SIGKILL.

     pdfork() returns a PID, 0 or -1, as fork(2) does.

     pdgetpid() and pdkill() return 0 on success and -1 on failure.

     pdwait4() returns a PID on success and -1 on failure.

     These functions may return the same error numbers as their PID-based
     equivalents (e.g.  pdfork() may return the same error numbers as
     fork(2)), with the following additions:

     [EINVAL]           The signal number given to pdkill() is invalid.

     [ENOTCAPABLE]      The process descriptor being operated on has
                        insufficient rights (e.g.  CAP_PDKILL for pdkill()).

     close(2), fork(2), fstat(2), kill(2), poll(2), wait4(2), capsicum(4),

     The pdfork(), pdgetpid(), pdkill() and pdwait4() system calls first
     appeared in FreeBSD 9.0.

     Support for process descriptors mode was developed as part of the
     TrustedBSD Project.

     These functions and the capability facility were created by Robert N. M.
     Watson <[email protected]> and Jonathan Anderson <[email protected]>
     at the University of Cambridge Computer Laboratory with support from a
     grant from Google, Inc.

     pdwait4() has not yet been implemented.

FreeBSD 11.1-RELEASE-p4          June 8, 2016          FreeBSD 11.1-RELEASE-p4
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