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pdfork(2freebsd)

October 14, 2018

freebsd-manpages

Manual pages for a GNU/kFreeBSD system

NAME

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

LIBRARY


.Lb libc

SYNOPSIS


.In sys/procdesc.h pid_t pdfork int *fdp int flags int pdgetpid int fd pid_t *pidp int pdkill int fd int signum

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 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 kill(2).
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.
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 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.

RETURN VALUES

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

HISTORY

The pdfork, pdgetpid, and pdkill system calls first appeared in
.Fx 9.0 .
Support for process descriptors mode was developed as part of the TrustedBSD Project.

AUTHORS


.An -nosplit These functions and the capability facility were created by
.An Robert N. M. Watson Aq Mt and
.An Jonathan Anderson Aq Mt at the University of Cambridge Computer Laboratory with support from a grant from Google, Inc.
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