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Man Pages


Manual Reference Pages  -  PDWAIT4 (2)

NAME

pdfork, pdgetpid, pdkill, pdwait4 - System calls to manage process descriptors

CONTENTS

Library
Synopsis
Description
Return Values
Errors
See Also
History
Authors
Bugs

LIBRARY


.Lb libc

SYNOPSIS


.In sys/procdesc.h int 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 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)).

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.

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.

pdfork and associated functions depend on
.Cd options PROCDESC described in procdesc(4).

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
.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 rwatson@FreeBSD.org and
.An Jonathan Anderson Aq jonathan@FreeBSD.org at the University of Cambridge Computer Laboratory with support from a grant from Google, Inc.

BUGS

pdwait4 has not yet been implemented.
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