October 14, 2018
pdfork, pdgetpid, pdkill - System calls to manage process descriptors
.In sys/procdesc.h pid_t
pdfork int *fdp int flagsint
pdgetpid int fd pid_t *pidpint
pdkill int fd int signum
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
pdforkwill not cause
pdforkcan accept the flags:
|Instead of the default terminate-on-close behaviour, allow the process to live until it is explicitly killed with kill(2).|
|Set close-on-exec on process descriptor.|
pdgetpidqueries the process ID (PID) in the process descriptor fd.
pdkillis functionally identical to kill(2), except that it accepts a process descriptor, fd, rather than a PID.
The following system calls also have effects specific to process descriptors:
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
POLLHUPis defined, and will be raised when the process dies. Process state transitions can also be monitored using kqueue(2) filter
EVFILT_PROCDESC; currently only
close(2) will close the process descriptor unless
PD_DAEMONis 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
pdforkreturns a PID, 0 or -1, as fork(2) does.
pdkillreturn 0 on success and -1 on failure.
These functions may return the same error numbers as their PID-based equivalents (e.g.
pdforkmay return the same error numbers as fork(2)), with the following additions:
|The signal number given to
|The process descriptor being operated on has insufficient rights (e.g.
.Fx 9.0 .
pdkillsystem calls first appeared in
.Fx 9.0 .
Support for process descriptors mode was developed as part of the TrustedBSD Project.