|Instead of the default terminate-on-close behaviour, allow the process to live until it is explicitly killed with kill(2).|
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 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.
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.
and associated functions depend on
.Cd options PROCDESC described in procdesc(4).
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).
The pdfork, pdgetpid, pdkill and pdwait4 system calls first appeared in
.Fx 9.0 .
Support for process descriptors mode was developed as part of the TrustedBSD Project.
.An -nosplit These functions and the capability facility were created by
.An Robert N. M. Watson Aq rwatson@FreeBSD.org and
.An Jonathan Anderson Aq jonathan@FreeBSD.org at the University of Cambridge Computer Laboratory with support from a grant from Google, Inc.
pdwait4 has not yet been implemented.