Copyright (c) 2009-2010, 2012-2013 Robert N. M. Watson All rights reserved. This software was developed at the University of Cambridge Computer Laboratory with support from a grant from Google, Inc. This software was developed by SRI International and the University of Cambridge Computer Laboratory under DARPA/AFRL contract (FA8750-10-C-0237) ("CTSRD"), as part of the DARPA CRASH research programme. Redistribution and use in source and binary forms, with or without modification, are permit...
NAMEpdfork pdgetpid pdkill pdwait4 - System calls to manage process descriptors
SYNOPSISIn sys/procdesc.h Ft pid_t Fn pdfork int *fdp int flags Ft int Fn pdgetpid int fd pid_t *pidp Ft int Fn pdkill int fd int signum Ft int Fn pdwait4 int fd int *status int options struct rusage *rusage
DESCRIPTIONProcess descriptors are special file descriptors that represent processes, and are created using Fn pdfork , a variant of fork(2), which, if successful, returns a process descriptor in the integer pointed to by Fa fdp . Processes created via Fn pdfork will not cause SIGCHLD on termination. Fn pdfork can accept the flags:
Instead of the default terminate-on-close behaviour, allow the process to
live until it is explicitly killed with
This option is not permitted in capsicum(4) capability mode (see cap_enter2).
- Set close-on-exec on process descriptor.
Fn pdgetpid queries the process ID (PID) in the process descriptor Fa fd .
Fn pdkill is functionally identical to kill(2), except that it accepts a process descriptor, Fa fd , rather than a PID.
Fn 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 Fa st_mode , Fa st_birthtime , Fa st_atime , Fa st_ctime and Fa 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 VALUESFn pdfork returns a PID, 0 or -1, as fork(2) does.
Fn pdgetpid and Fn pdkill return 0 on success and -1 on failure.
Fn pdwait4 returns a PID on success and -1 on failure.
ERRORSThese functions may return the same error numbers as their PID-based equivalents (e.g. Fn pdfork may return the same error numbers as fork(2)), with the following additions:
- Bq Er EINVAL
- The signal number given to Fn pdkill is invalid.
- Bq Er ENOTCAPABLE
- The process descriptor being operated on has insufficient rights (e.g. CAP_PDKILL for Fn pdkill ) .
SEE ALSOclose(2), fork(2), fstat(2), kill(2), poll(2), wait4(2), capsicum(4), procdesc(4)
HISTORYThe Fn pdfork , Fn pdgetpid , Fn pdkill and Fn pdwait4 system calls first appeared in Fx 9.0 .
Support for process descriptors mode was developed as part of the TrustedBSD Project.