|PDFORK(2)||System Calls Manual||PDFORK(2)|
LIBRARY¶Standard C Library (libc, -lc)
DESCRIPTION¶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
pdfork() can 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.
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.
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
POLLHUP is defined, and will be raised when the
process dies. Process state transitions can also be monitored using
NOTE_EXIT is implemented.
close(2) will close the process descriptor
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
pdfork() returns a PID, 0 or -1, as fork(2) does.
pdkill() return 0 on success and -1 on failure.
ERRORS¶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:
SEE ALSO¶close(2), fork(2), fstat(2), kill(2), poll(2), kqueue(2), wait4(2), capsicum(4), procdesc(4)
pdkill() system calls first appeared in FreeBSD 9.0.
Support for process descriptors mode was developed as part of the TrustedBSD Project.
AUTHORS¶These functions and the capability facility were created by Robert N. M. Watson <rwatson@FreeBSD.org> and Jonathan Anderson <jonathan@FreeBSD.org> at the University of Cambridge Computer Laboratory with support from a grant from Google, Inc.
|October 14, 2018||Linux 4.9.0-9-amd64|