|PDFORK(2)||System Calls Manual||PDFORK(2)|
System calls to manage process descriptors
Standard C Library (libc, -lc)
fd, int *status,
Process descriptors are special file descriptors that represent
processes, and are created using
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:
- 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.
queries the process ID (PID) in the process descriptor
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
pdkill() return 0 on success and -1 on failure.
pdwait4() returns a PID on success and -1
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
pdwait4() system calls first appeared in
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 <rwatson@FreeBSD.org> and Jonathan Anderson <jonathan@FreeBSD.org> at the University of Cambridge Computer Laboratory with support from a grant from Google, Inc.
pdwait4() has not yet been
|June 8, 2016||Debian|