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procdesc(4) [freebsd man page]

PROCDESC(4)						   BSD Kernel Interfaces Manual 					       PROCDESC(4)

procdesc -- process descriptor facility DESCRIPTION
procdesc is a file-descriptor-oriented interface to process signalling and control, which supplements historic UNIX fork(2), kill(2), and wait4(2) primitives with new system calls such as pdfork(2), pdkill(2), and pdwait4(2). procdesc is designed for use with capsicum(4), replacing process identifiers with capability-oriented references. However, it can also be used independently of capsicum(4), displacing PIDs, which may otherwise suffer from race conditions. Given a process descriptor, it is possible to query its conventional PID using pdgetpid(2). SEE ALSO
fork(2), kill(2), pdfork(2), pdgetpid(2), pdkill(2), pdwait4(2), wait4(2), capsicum(4) HISTORY
procdesc first appeared in FreeBSD 9.0, and was developed at the University of Cambridge. AUTHORS
procdesc was developed by Robert Watson <> and Jonathan Anderson <> at the University of Cambridge, and Ben Laurie <> and Kris Kennaway <> at Google, Inc. BUGS
procdesc is considered experimental in FreeBSD. BSD
August 21, 2013 BSD

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PDFORK(2)						      BSD System Calls Manual							 PDFORK(2)

pdfork, pdgetpid, pdkill, pdwait4 -- System calls to manage process descriptors LIBRARY
Standard C Library (libc, -lc) SYNOPSIS
#include <sys/procdesc.h> pid_t pdfork(int *fdp, int flags); int pdgetpid(int fd, pid_t *pidp); int pdkill(int fd, int signum); int pdwait4(int fd, int *status, int options, struct rusage *rusage); 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 termina- tion. 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)). 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. 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. pdwait4() returns a PID 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()). SEE ALSO
close(2), fork(2), fstat(2), kill(2), poll(2), wait4(2), capsicum(4), procdesc(4) HISTORY
The pdfork(), pdgetpid(), pdkill() and pdwait4() 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 <> and Jonathan Anderson <> at the University of Cambridge Computer Laboratory with support from a grant from Google, Inc. BUGS
pdwait4() has not yet been implemented. BSD
April 7, 2014 BSD

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