1 # SOME DESCRIPTIVE TITLE
2 # Copyright (C) YEAR Free Software Foundation, Inc.
3 # This file is distributed under the same license as the PACKAGE package.
4 # FIRST AUTHOR <EMAIL@ADDRESS>, YEAR.
9 "Project-Id-Version: PACKAGE VERSION\n"
10 "POT-Creation-Date: 2014-04-13 10:27+0900\n"
11 "PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n"
12 "Last-Translator: FULL NAME <EMAIL@ADDRESS>\n"
13 "Language-Team: LANGUAGE <LL@li.org>\n"
16 "Content-Type: text/plain; charset=UTF-8\n"
17 "Content-Transfer-Encoding: 8bit\n"
20 #: build/C/man3/mq_close.3:26
26 #: build/C/man3/mq_close.3:26 build/C/man3/mq_getattr.3:26 build/C/man3/mq_unlink.3:26
32 #: build/C/man3/mq_close.3:26 build/C/man3/mq_getattr.3:26 build/C/man2/mq_getsetattr.2:26 build/C/man3/mq_notify.3:26 build/C/man3/mq_open.3:26 build/C/man7/mq_overview.7:26 build/C/man3/mq_receive.3:26 build/C/man3/mq_send.3:26 build/C/man3/mq_unlink.3:26 build/C/man2/msgctl.2:37 build/C/man2/msgget.2:35 build/C/man2/msgop.2:40
38 #: build/C/man3/mq_close.3:26 build/C/man3/mq_getattr.3:26 build/C/man2/mq_getsetattr.2:26 build/C/man3/mq_notify.3:26 build/C/man3/mq_open.3:26 build/C/man7/mq_overview.7:26 build/C/man3/mq_receive.3:26 build/C/man3/mq_send.3:26 build/C/man3/mq_unlink.3:26 build/C/man2/msgctl.2:37 build/C/man2/msgget.2:35 build/C/man2/msgop.2:40
40 msgid "Linux Programmer's Manual"
44 #: build/C/man3/mq_close.3:27 build/C/man3/mq_getattr.3:27 build/C/man2/mq_getsetattr.2:27 build/C/man3/mq_notify.3:27 build/C/man3/mq_open.3:27 build/C/man7/mq_overview.7:27 build/C/man3/mq_receive.3:27 build/C/man3/mq_send.3:27 build/C/man3/mq_unlink.3:27 build/C/man2/msgctl.2:38 build/C/man2/msgget.2:36 build/C/man2/msgop.2:41
50 #: build/C/man3/mq_close.3:29
51 msgid "mq_close - close a message queue descriptor"
55 #: build/C/man3/mq_close.3:29 build/C/man3/mq_getattr.3:29 build/C/man2/mq_getsetattr.2:29 build/C/man3/mq_notify.3:29 build/C/man3/mq_open.3:29 build/C/man3/mq_receive.3:29 build/C/man3/mq_send.3:29 build/C/man3/mq_unlink.3:29 build/C/man2/msgctl.2:40 build/C/man2/msgget.2:38 build/C/man2/msgop.2:43
61 #: build/C/man3/mq_close.3:32 build/C/man3/mq_getattr.3:32 build/C/man3/mq_notify.3:32 build/C/man3/mq_receive.3:32 build/C/man3/mq_send.3:32 build/C/man3/mq_unlink.3:32
63 msgid "B<#include E<lt>mqueue.hE<gt>>\n"
67 #: build/C/man3/mq_close.3:34
69 msgid "B<int mq_close(mqd_t >I<mqdes>B<);>\n"
73 #: build/C/man3/mq_close.3:37 build/C/man3/mq_getattr.3:40 build/C/man3/mq_notify.3:37 build/C/man3/mq_open.3:41 build/C/man3/mq_receive.3:45 build/C/man3/mq_send.3:45 build/C/man3/mq_unlink.3:37
74 msgid "Link with I<-lrt>."
78 #: build/C/man3/mq_close.3:37 build/C/man3/mq_getattr.3:40 build/C/man2/mq_getsetattr.2:40 build/C/man3/mq_notify.3:37 build/C/man3/mq_open.3:41 build/C/man7/mq_overview.7:29 build/C/man3/mq_receive.3:57 build/C/man3/mq_send.3:57 build/C/man3/mq_unlink.3:37 build/C/man2/msgctl.2:48 build/C/man2/msgget.2:46 build/C/man2/msgop.2:56
84 #: build/C/man3/mq_close.3:41
85 msgid "B<mq_close>() closes the message queue descriptor I<mqdes>."
89 #: build/C/man3/mq_close.3:47
91 "If the calling process has attached a notification request to this message "
92 "queue via I<mqdes>, then this request is removed, and another process can "
93 "now attach a notification request."
97 #: build/C/man3/mq_close.3:47 build/C/man3/mq_getattr.3:118 build/C/man3/mq_notify.3:134 build/C/man3/mq_open.3:123 build/C/man3/mq_receive.3:113 build/C/man3/mq_send.3:119 build/C/man3/mq_unlink.3:44 build/C/man2/msgctl.2:229 build/C/man2/msgget.2:137 build/C/man2/msgop.2:321
103 #: build/C/man3/mq_close.3:53
105 "On success B<mq_close>() returns 0; on error, -1 is returned, with I<errno> "
106 "set to indicate the error."
110 #: build/C/man3/mq_close.3:53 build/C/man3/mq_getattr.3:126 build/C/man3/mq_notify.3:140 build/C/man3/mq_open.3:135 build/C/man3/mq_receive.3:122 build/C/man3/mq_send.3:127 build/C/man3/mq_unlink.3:50 build/C/man2/msgctl.2:254 build/C/man2/msgget.2:143 build/C/man2/msgop.2:334
116 #: build/C/man3/mq_close.3:54 build/C/man3/mq_getattr.3:127 build/C/man3/mq_notify.3:141 build/C/man3/mq_receive.3:129 build/C/man3/mq_send.3:134
122 #: build/C/man3/mq_close.3:59 build/C/man3/mq_getattr.3:132 build/C/man3/mq_notify.3:146
123 msgid "The descriptor specified in I<mqdes> is invalid."
127 #: build/C/man3/mq_close.3:59 build/C/man3/mq_getattr.3:137 build/C/man2/mq_getsetattr.2:50 build/C/man3/mq_notify.3:174 build/C/man3/mq_open.3:224 build/C/man7/mq_overview.7:263 build/C/man3/mq_receive.3:156 build/C/man3/mq_send.3:161 build/C/man3/mq_unlink.3:62 build/C/man2/msgctl.2:325 build/C/man2/msgget.2:183 build/C/man2/msgop.2:464
129 msgid "CONFORMING TO"
133 #: build/C/man3/mq_close.3:61 build/C/man3/mq_getattr.3:139 build/C/man3/mq_notify.3:176 build/C/man3/mq_open.3:226 build/C/man7/mq_overview.7:265 build/C/man3/mq_receive.3:158 build/C/man3/mq_send.3:163 build/C/man3/mq_unlink.3:64
134 msgid "POSIX.1-2001."
138 #: build/C/man3/mq_close.3:61 build/C/man3/mq_getattr.3:139 build/C/man2/mq_getsetattr.2:52 build/C/man7/mq_overview.7:265 build/C/man3/mq_receive.3:158 build/C/man3/mq_send.3:163 build/C/man2/msgctl.2:328 build/C/man2/msgget.2:185 build/C/man2/msgop.2:476
144 #: build/C/man3/mq_close.3:65
146 "All open message queues are automatically closed on process termination, or "
151 #: build/C/man3/mq_close.3:65 build/C/man3/mq_getattr.3:147 build/C/man2/mq_getsetattr.2:56 build/C/man3/mq_notify.3:243 build/C/man3/mq_open.3:230 build/C/man7/mq_overview.7:281 build/C/man3/mq_receive.3:164 build/C/man3/mq_send.3:169 build/C/man3/mq_unlink.3:64 build/C/man2/msgctl.2:367 build/C/man2/msgget.2:230 build/C/man2/msgop.2:557
157 #: build/C/man3/mq_close.3:73
159 "B<mq_getattr>(3), B<mq_notify>(3), B<mq_open>(3), B<mq_receive>(3), "
160 "B<mq_send>(3), B<mq_unlink>(3), B<mq_overview>(7)"
164 #: build/C/man3/mq_close.3:73 build/C/man3/mq_getattr.3:155 build/C/man2/mq_getsetattr.2:59 build/C/man3/mq_notify.3:252 build/C/man3/mq_open.3:238 build/C/man7/mq_overview.7:294 build/C/man3/mq_receive.3:173 build/C/man3/mq_send.3:178 build/C/man3/mq_unlink.3:72 build/C/man2/msgctl.2:374 build/C/man2/msgget.2:238 build/C/man2/msgop.2:563
170 #: build/C/man3/mq_close.3:80 build/C/man3/mq_getattr.3:162 build/C/man2/mq_getsetattr.2:66 build/C/man3/mq_notify.3:259 build/C/man3/mq_open.3:245 build/C/man7/mq_overview.7:301 build/C/man3/mq_receive.3:180 build/C/man3/mq_send.3:185 build/C/man3/mq_unlink.3:79 build/C/man2/msgctl.2:381 build/C/man2/msgget.2:245 build/C/man2/msgop.2:570
172 "This page is part of release 3.63 of the Linux I<man-pages> project. A "
173 "description of the project, and information about reporting bugs, can be "
174 "found at \\%http://www.kernel.org/doc/man-pages/."
178 #: build/C/man3/mq_getattr.3:26
184 #: build/C/man3/mq_getattr.3:29
185 msgid "mq_getattr, mq_setattr - get/set message queue attributes"
189 #: build/C/man3/mq_getattr.3:34
191 msgid "B<int mq_getattr(mqd_t >I<mqdes>B<, struct mq_attr *>I<attr>B<);>\n"
195 #: build/C/man3/mq_getattr.3:37
198 "B<int mq_setattr(mqd_t >I<mqdes>B<, struct mq_attr *>I<newattr>B<,>\n"
199 "B< struct mq_attr *>I<oldattr>B<);>\n"
203 #: build/C/man3/mq_getattr.3:47
205 "B<mq_getattr>() and B<mq_setattr>() respectively retrieve and modify "
206 "attributes of the message queue referred to by the descriptor I<mqdes>."
210 #: build/C/man3/mq_getattr.3:54
212 "B<mq_getattr>() returns an I<mq_attr> structure in the buffer pointed by "
213 "I<attr>. This structure is defined as:"
217 #: build/C/man3/mq_getattr.3:63
221 " long mq_flags; /* Flags: 0 or O_NONBLOCK */\n"
222 " long mq_maxmsg; /* Max. # of messages on queue */\n"
223 " long mq_msgsize; /* Max. message size (bytes) */\n"
224 " long mq_curmsgs; /* # of messages currently in queue */\n"
229 #: build/C/man3/mq_getattr.3:73
231 "The I<mq_flags> field contains flags associated with the open message queue "
232 "description. This field is initialized when the queue is created by "
233 "B<mq_open>(3). The only flag that can appear in this field is "
238 #: build/C/man3/mq_getattr.3:94
240 "The I<mq_maxmsg> and I<mq_msgsize> fields are set when the message queue is "
241 "created by B<mq_open>(3). The I<mq_maxmsg> field is an upper limit on the "
242 "number of messages that may be placed on the queue using B<mq_send>(3). The "
243 "I<mq_msgsize> field is an upper limit on the size of messages that may be "
244 "placed on the queue. Both of these fields must have a value greater than "
245 "zero. Two I</proc> files that place ceilings on the values for these fields "
246 "are described in B<mq_open>(3)."
250 #: build/C/man3/mq_getattr.3:98
252 "The I<mq_curmsgs> field returns the number of messages currently held in the "
257 #: build/C/man3/mq_getattr.3:118
259 "B<mq_setattr>() sets message queue attributes using information supplied in "
260 "the I<mq_attr> structure pointed to by I<newattr>. The only attribute that "
261 "can be modified is the setting of the B<O_NONBLOCK> flag in I<mq_flags>. "
262 "The other fields in I<newattr> are ignored. If the I<oldattr> field is not "
263 "NULL, then the buffer that it points to is used to return an I<mq_attr> "
264 "structure that contains the same information that is returned by "
269 #: build/C/man3/mq_getattr.3:126
271 "On success B<mq_getattr>() and B<mq_setattr>() return 0; on error, -1 is "
272 "returned, with I<errno> set to indicate the error."
276 #: build/C/man3/mq_getattr.3:132 build/C/man3/mq_notify.3:150 build/C/man3/mq_open.3:156 build/C/man3/mq_receive.3:138 build/C/man3/mq_send.3:143 build/C/man2/msgctl.2:285 build/C/man2/msgop.2:365 build/C/man2/msgop.2:421
282 #: build/C/man3/mq_getattr.3:137
283 msgid "I<newattr-E<gt>mq_flags> contained set bits other than B<O_NONBLOCK>."
287 #: build/C/man3/mq_getattr.3:147
289 "On Linux, B<mq_getattr>() and B<mq_setattr>() are library functions "
290 "layered on top of the B<mq_getsetattr>(2) system call."
294 #: build/C/man3/mq_getattr.3:155
296 "B<mq_close>(3), B<mq_notify>(3), B<mq_open>(3), B<mq_receive>(3), "
297 "B<mq_send>(3), B<mq_unlink>(3), B<mq_overview>(7)"
301 #: build/C/man2/mq_getsetattr.2:26
303 msgid "MQ_GETSETATTR"
307 #: build/C/man2/mq_getsetattr.2:26
313 #: build/C/man2/mq_getsetattr.2:29
314 msgid "mq_getsetattr - get/set message queue attributes"
318 #: build/C/man2/mq_getsetattr.2:33
321 "B<#include E<lt>sys/types.hE<gt>>\n"
322 "B<#include E<lt>mqueue.hE<gt>>\n"
326 #: build/C/man2/mq_getsetattr.2:36
329 "B<int mq_getsetattr(mqd_t >I<mqdes>B<, struct mq_attr *>I<newattr>B<,>\n"
330 "B< struct mq_attr *>I<oldattr>B<);>\n"
334 #: build/C/man2/mq_getsetattr.2:40
335 msgid "I<Note>: There is no glibc wrapper for this system call; see NOTES."
339 #: build/C/man2/mq_getsetattr.2:42
340 msgid "Do not use this system call."
344 #: build/C/man2/mq_getsetattr.2:50
346 "This is the low-level system call used to implement B<mq_getattr>(3) and "
347 "B<mq_setattr>(3). For an explanation of how this system call operates, see "
348 "the description of B<mq_setattr>(3)."
352 #: build/C/man2/mq_getsetattr.2:52
353 msgid "This interface is nonstandard; avoid its use."
357 #: build/C/man2/mq_getsetattr.2:56
359 "Glibc does not provide a wrapper for this system call; call it using "
360 "B<syscall>(2). (Actually, never call it unless you are writing a C "
365 #: build/C/man2/mq_getsetattr.2:59
366 msgid "B<mq_getattr>(3), B<mq_overview>(7)"
370 #: build/C/man3/mq_notify.3:26
376 #: build/C/man3/mq_notify.3:26
382 #: build/C/man3/mq_notify.3:29
383 msgid "mq_notify - register for notification when a message is available"
387 #: build/C/man3/mq_notify.3:34
389 msgid "B<int mq_notify(mqd_t >I<mqdes>B<, const struct sigevent *>I<sevp>B<);>\n"
393 #: build/C/man3/mq_notify.3:43
395 "B<mq_notify>() allows the calling process to register or unregister for "
396 "delivery of an asynchronous notification when a new message arrives on the "
397 "empty message queue referred to by the descriptor I<mqdes>."
401 #: build/C/man3/mq_notify.3:51
403 "The I<sevp> argument is a pointer to a I<sigevent> structure. For the "
404 "definition and general details of this structure, see B<sigevent>(7)."
408 #: build/C/man3/mq_notify.3:65
410 "If I<sevp> is a non-null pointer, then B<mq_notify>() registers the calling "
411 "process to receive message notification. The I<sigev_notify> field of the "
412 "I<sigevent> structure to which I<sevp> points specifies how notification is "
413 "to be performed. This field has one of the following values:"
417 #: build/C/man3/mq_notify.3:65
419 msgid "B<SIGEV_NONE>"
422 #. When is SIGEV_NONE useful?
424 #: build/C/man3/mq_notify.3:70
426 "A \"null\" notification: the calling process is registered as the target for "
427 "notification, but when a message arrives, no notification is sent."
431 #: build/C/man3/mq_notify.3:70
433 msgid "B<SIGEV_SIGNAL>"
436 #. I don't know of other implementations that set
437 #. si_pid and si_uid -- MTK
439 #: build/C/man3/mq_notify.3:90
441 "Notify the process by sending the signal specified in I<sigev_signo>. See "
442 "B<sigevent>(7) for general details. The I<si_code> field of the "
443 "I<siginfo_t> structure will be set to B<SI_MESGQ>. In addition, I<si_pid> "
444 "will be set to the PID of the process that sent the message, and I<si_uid> "
445 "will be set to the real user ID of the sending process."
449 #: build/C/man3/mq_notify.3:90
451 msgid "B<SIGEV_THREAD>"
455 #: build/C/man3/mq_notify.3:98
457 "Upon message delivery, invoke I<sigev_notify_function> as if it were the "
458 "start function of a new thread. See B<sigevent>(7) for details."
462 #: build/C/man3/mq_notify.3:101
464 "Only one process can be registered to receive notification from a message "
469 #: build/C/man3/mq_notify.3:108
471 "If I<sevp> is NULL, and the calling process is currently registered to "
472 "receive notifications for this message queue, then the registration is "
473 "removed; another process can then register to receive a message notification "
478 #: build/C/man3/mq_notify.3:115
480 "Message notification occurs only when a new message arrives and the queue "
481 "was previously empty. If the queue was not empty at the time B<mq_notify>() "
482 "was called, then a notification will occur only after the queue is emptied "
483 "and a new message arrives."
487 #: build/C/man3/mq_notify.3:123
489 "If another process or thread is waiting to read a message from an empty "
490 "queue using B<mq_receive>(3), then any message notification registration is "
491 "ignored: the message is delivered to the process or thread calling "
492 "B<mq_receive>(3), and the message notification registration remains in "
497 #: build/C/man3/mq_notify.3:134
499 "Notification occurs once: after a notification is delivered, the "
500 "notification registration is removed, and another process can register for "
501 "message notification. If the notified process wishes to receive the next "
502 "notification, it can use B<mq_notify>() to request a further notification. "
503 "This should be done before emptying all unread messages from the queue. "
504 "(Placing the queue in nonblocking mode is useful for emptying the queue of "
505 "messages without blocking once it is empty.)"
509 #: build/C/man3/mq_notify.3:140
511 "On success B<mq_notify>() returns 0; on error, -1 is returned, with "
512 "I<errno> set to indicate the error."
516 #: build/C/man3/mq_notify.3:146
522 #: build/C/man3/mq_notify.3:150
524 "Another process has already registered to receive notification for this "
529 #: build/C/man3/mq_notify.3:160
531 "I<sevp-E<gt>sigev_notify> is not one of the permitted values; or "
532 "I<sevp-E<gt>sigev_notify> is B<SIGEV_SIGNAL> and I<sevp-E<gt>sigev_signo> is "
533 "not a valid signal number."
537 #: build/C/man3/mq_notify.3:160 build/C/man3/mq_open.3:214 build/C/man2/msgget.2:173 build/C/man2/msgop.2:376
543 #: build/C/man3/mq_notify.3:163 build/C/man3/mq_open.3:217
544 msgid "Insufficient memory."
547 #. Linux does not do this
549 #: build/C/man3/mq_notify.3:174
551 "POSIX.1-2008 says that an implementation I<may> generate an B<EINVAL> error "
552 "if I<sevp> is NULL, and the caller is not currently registered to receive "
553 "notifications for the queue I<mqdes>."
557 #: build/C/man3/mq_notify.3:176 build/C/man7/mq_overview.7:278
563 #: build/C/man3/mq_notify.3:182
565 "The following program registers a notification request for the message queue "
566 "named in its command-line argument. Notification is performed by creating a "
567 "thread. The thread executes a function which reads one message from the "
568 "queue and then terminates the process."
572 #: build/C/man3/mq_notify.3:182
574 msgid "Program source"
578 #: build/C/man3/mq_notify.3:189
581 "#include E<lt>pthread.hE<gt>\n"
582 "#include E<lt>mqueue.hE<gt>\n"
583 "#include E<lt>stdio.hE<gt>\n"
584 "#include E<lt>stdlib.hE<gt>\n"
585 "#include E<lt>unistd.hE<gt>\n"
589 #: build/C/man3/mq_notify.3:192
592 "#define handle_error(msg) \\e\n"
593 " do { perror(msg); exit(EXIT_FAILURE); } while (0)\n"
597 #: build/C/man3/mq_notify.3:200
600 "static void /* Thread start function */\n"
601 "tfunc(union sigval sv)\n"
603 " struct mq_attr attr;\n"
606 " mqd_t mqdes = *((mqd_t *) sv.sival_ptr);\n"
610 #: build/C/man3/mq_notify.3:202
612 msgid " /* Determine max. msg size; allocate buffer to receive msg */\n"
616 #: build/C/man3/mq_notify.3:208
619 " if (mq_getattr(mqdes, &attr) == -1)\n"
620 " handle_error(\"mq_getattr\");\n"
621 " buf = malloc(attr.mq_msgsize);\n"
622 " if (buf == NULL)\n"
623 " handle_error(\"malloc\");\n"
627 #: build/C/man3/mq_notify.3:212
630 " nr = mq_receive(mqdes, buf, attr.mq_msgsize, NULL);\n"
632 " handle_error(\"mq_receive\");\n"
636 #: build/C/man3/mq_notify.3:217
639 " printf(\"Read %ld bytes from MQ\\en\", (long) nr);\n"
641 " exit(EXIT_SUCCESS); /* Terminate the process */\n"
646 #: build/C/man3/mq_notify.3:223
650 "main(int argc, char *argv[])\n"
653 " struct sigevent sev;\n"
657 #: build/C/man3/mq_notify.3:228
660 " if (argc != 2) {\n"
661 " fprintf(stderr, \"Usage: %s E<lt>mq-nameE<gt>\\en\", argv[0]);\n"
662 " exit(EXIT_FAILURE);\n"
667 #: build/C/man3/mq_notify.3:232
670 " mqdes = mq_open(argv[1], O_RDONLY);\n"
671 " if (mqdes == (mqd_t) -1)\n"
672 " handle_error(\"mq_open\");\n"
676 #: build/C/man3/mq_notify.3:239
679 " sev.sigev_notify = SIGEV_THREAD;\n"
680 " sev.sigev_notify_function = tfunc;\n"
681 " sev.sigev_notify_attributes = NULL;\n"
682 " sev.sigev_value.sival_ptr = &mqdes; /* Arg. to thread func. */\n"
683 " if (mq_notify(mqdes, &sev) == -1)\n"
684 " handle_error(\"mq_notify\");\n"
688 #: build/C/man3/mq_notify.3:242
691 " pause(); /* Process will be terminated by thread function */\n"
696 #: build/C/man3/mq_notify.3:252
698 "B<mq_close>(3), B<mq_getattr>(3), B<mq_open>(3), B<mq_receive>(3), "
699 "B<mq_send>(3), B<mq_unlink>(3), B<mq_overview>(7), B<sigevent>(7)"
703 #: build/C/man3/mq_open.3:26
709 #: build/C/man3/mq_open.3:26
715 #: build/C/man3/mq_open.3:29
716 msgid "mq_open - open a message queue"
720 #: build/C/man3/mq_open.3:34
723 "B<#include E<lt>fcntl.hE<gt>> /* For O_* constants */\n"
724 "B<#include E<lt>sys/stat.hE<gt>> /* For mode constants */\n"
725 "B<#include E<lt>mqueue.hE<gt>>\n"
729 #: build/C/man3/mq_open.3:38
732 "B<mqd_t mq_open(const char *>I<name>B<, int >I<oflag>B<);>\n"
733 "B<mqd_t mq_open(const char *>I<name>B<, int >I<oflag>B<, mode_t "
735 "B< struct mq_attr *>I<attr>B<);>\n"
739 #: build/C/man3/mq_open.3:50
741 "B<mq_open>() creates a new POSIX message queue or opens an existing queue. "
742 "The queue is identified by I<name>. For details of the construction of "
743 "I<name>, see B<mq_overview>(7)."
747 #: build/C/man3/mq_open.3:58
749 "The I<oflag> argument specifies flags that control the operation of the "
750 "call. (Definitions of the flags values can be obtained by including "
751 "I<E<lt>fcntl.hE<gt>>.) Exactly one of the following must be specified in "
756 #: build/C/man3/mq_open.3:58
762 #: build/C/man3/mq_open.3:61
763 msgid "Open the queue to receive messages only."
767 #: build/C/man3/mq_open.3:61
773 #: build/C/man3/mq_open.3:64
774 msgid "Open the queue to send messages only."
778 #: build/C/man3/mq_open.3:64
784 #: build/C/man3/mq_open.3:67
785 msgid "Open the queue to both send and receive messages."
789 #: build/C/man3/mq_open.3:72
790 msgid "Zero or more of the following flags can additionally be I<OR>ed in I<oflag>:"
794 #: build/C/man3/mq_open.3:72
796 msgid "B<O_NONBLOCK>"
800 #: build/C/man3/mq_open.3:81
802 "Open the queue in nonblocking mode. In circumstances where B<mq_receive>(3) "
803 "and B<mq_send>(3) would normally block, these functions instead fail with "
804 "the error B<EAGAIN>."
808 #: build/C/man3/mq_open.3:81
813 #. In reality the filesystem IDs are used on Linux.
815 #: build/C/man3/mq_open.3:89
817 "Create the message queue if it does not exist. The owner (user ID) of the "
818 "message queue is set to the effective user ID of the calling process. The "
819 "group ownership (group ID) is set to the effective group ID of the calling "
824 #: build/C/man3/mq_open.3:89
830 #: build/C/man3/mq_open.3:99
832 "If B<O_CREAT> was specified in I<oflag>, and a queue with the given I<name> "
833 "already exists, then fail with the error B<EEXIST>."
837 #: build/C/man3/mq_open.3:123
839 "If B<O_CREAT> is specified in I<oflag>, then two additional arguments must "
840 "be supplied. The I<mode> argument specifies the permissions to be placed on "
841 "the new queue, as for B<open>(2). (Symbolic definitions for the permissions "
842 "bits can be obtained by including I<E<lt>sys/stat.hE<gt>>.) The permissions "
843 "settings are masked against the process umask. The I<attr> argument "
844 "specifies attributes for the queue. See B<mq_getattr>(3) for details. If "
845 "I<attr> is NULL, then the queue is created with implementation-defined "
846 "default attributes."
850 #: build/C/man3/mq_open.3:135
852 "On success, B<mq_open>() returns a message queue descriptor for use by "
853 "other message queue functions. On error, B<mq_open>() returns I<(mqd_t)\\ "
854 "-1>, with I<errno> set to indicate the error."
858 #: build/C/man3/mq_open.3:136 build/C/man3/mq_open.3:140 build/C/man3/mq_unlink.3:51 build/C/man2/msgctl.2:258 build/C/man2/msgget.2:147 build/C/man2/msgop.2:340 build/C/man2/msgop.2:395
864 #: build/C/man3/mq_open.3:140
866 "The queue exists, but the caller does not have permission to open it in the "
870 #. Note that this isn't consistent with the same case for sem_open()
872 #: build/C/man3/mq_open.3:145
873 msgid "I<name> contained more than one slash."
877 #: build/C/man3/mq_open.3:145 build/C/man2/msgget.2:155
883 #: build/C/man3/mq_open.3:156
885 "Both B<O_CREAT> and B<O_EXCL> were specified in I<oflag>, but a queue with "
886 "this I<name> already exists."
890 #: build/C/man3/mq_open.3:188
892 "B<O_CREAT> was specified in I<oflag>, and I<attr> was not NULL, but "
893 "I<attr-E<gt>mq_maxmsg> or I<attr-E<gt>mq_msqsize> was invalid. Both of "
894 "these fields must be greater than zero. In a process that is unprivileged "
895 "(does not have the B<CAP_SYS_RESOURCE> capability), I<attr-E<gt>mq_maxmsg> "
896 "must be less than or equal to the I<msg_max> limit, and "
897 "I<attr-E<gt>mq_msgsize> must be less than or equal to the I<msgsize_max> "
898 "limit. In addition, even in a privileged process, I<attr-E<gt>mq_maxmsg> "
899 "cannot exceed the B<HARD_MAX> limit. (See B<mq_overview>(7) for details of "
904 #: build/C/man3/mq_open.3:188
910 #: build/C/man3/mq_open.3:192
911 msgid "The process already has the maximum number of files and message queues open."
915 #: build/C/man3/mq_open.3:192 build/C/man3/mq_unlink.3:54
917 msgid "B<ENAMETOOLONG>"
921 #: build/C/man3/mq_open.3:196 build/C/man3/mq_unlink.3:58
922 msgid "I<name> was too long."
926 #: build/C/man3/mq_open.3:196
932 #: build/C/man3/mq_open.3:200
934 "The system limit on the total number of open files and message queues has "
939 #: build/C/man3/mq_open.3:200 build/C/man3/mq_open.3:209 build/C/man3/mq_unlink.3:58 build/C/man2/msgget.2:165
945 #: build/C/man3/mq_open.3:209
947 "The B<O_CREAT> flag was not specified in I<oflag>, and no queue with this "
951 #. Note that this isn't consistent with the same case for sem_open()
953 #: build/C/man3/mq_open.3:214
954 msgid "I<name> was just \"/\" followed by no other characters."
958 #: build/C/man3/mq_open.3:217 build/C/man2/msgget.2:177
964 #: build/C/man3/mq_open.3:224
966 "Insufficient space for the creation of a new message queue. This probably "
967 "occurred because the I<queues_max> limit was encountered; see "
972 #: build/C/man3/mq_open.3:226 build/C/man2/msgget.2:224 build/C/man2/msgop.2:521
978 #: build/C/man3/mq_open.3:230
980 "In kernels before 2.6.14, the process umask was not applied to the "
981 "permissions specified in I<mode>."
985 #: build/C/man3/mq_open.3:238
987 "B<mq_close>(3), B<mq_getattr>(3), B<mq_notify>(3), B<mq_receive>(3), "
988 "B<mq_send>(3), B<mq_unlink>(3), B<mq_overview>(7)"
992 #: build/C/man7/mq_overview.7:26
998 #: build/C/man7/mq_overview.7:26
1004 #: build/C/man7/mq_overview.7:29
1005 msgid "mq_overview - overview of POSIX message queues"
1009 #: build/C/man7/mq_overview.7:37
1011 "POSIX message queues allow processes to exchange data in the form of "
1012 "messages. This API is distinct from that provided by System V message "
1013 "queues (B<msgget>(2), B<msgsnd>(2), B<msgrcv>(2), etc.), but provides "
1014 "similar functionality."
1018 #: build/C/man7/mq_overview.7:52
1020 "Message queues are created and opened using B<mq_open>(3); this function "
1021 "returns a I<message queue descriptor> (I<mqd_t>), which is used to refer to "
1022 "the open message queue in later calls. Each message queue is identified by "
1023 "a name of the form I</somename>; that is, a null-terminated string of up to "
1024 "B<NAME_MAX> (i.e., 255) characters consisting of an initial slash, followed "
1025 "by one or more characters, none of which are slashes. Two processes can "
1026 "operate on the same queue by passing the same name to B<mq_open>(3)."
1030 #: build/C/man7/mq_overview.7:68
1032 "Messages are transferred to and from a queue using B<mq_send>(3) and "
1033 "B<mq_receive>(3). When a process has finished using the queue, it closes it "
1034 "using B<mq_close>(3), and when the queue is no longer required, it can be "
1035 "deleted using B<mq_unlink>(3). Queue attributes can be retrieved and (in "
1036 "some cases) modified using B<mq_getattr>(3) and B<mq_setattr>(3). A "
1037 "process can request asynchronous notification of the arrival of a message on "
1038 "a previously empty queue using B<mq_notify>(3)."
1042 #: build/C/man7/mq_overview.7:81
1044 "A message queue descriptor is a reference to an I<open message queue "
1045 "description> (cf. B<open>(2)). After a B<fork>(2), a child inherits copies "
1046 "of its parent's message queue descriptors, and these descriptors refer to "
1047 "the same open message queue descriptions as the corresponding descriptors in "
1048 "the parent. Corresponding descriptors in the two processes share the flags "
1049 "(I<mq_flags>) that are associated with the open message queue description."
1053 #: build/C/man7/mq_overview.7:94
1055 "Each message has an associated I<priority>, and messages are always "
1056 "delivered to the receiving process highest priority first. Message "
1057 "priorities range from 0 (low) to I<sysconf(_SC_MQ_PRIO_MAX)\\ -\\ 1> "
1058 "(high). On Linux, I<sysconf(_SC_MQ_PRIO_MAX)> returns 32768, but "
1059 "POSIX.1-2001 requires only that an implementation support at least "
1060 "priorities in the range 0 to 31; some implementations provide only this "
1065 #: build/C/man7/mq_overview.7:97
1067 "The remainder of this section describes some specific details of the Linux "
1068 "implementation of POSIX message queues."
1072 #: build/C/man7/mq_overview.7:97
1074 msgid "Library interfaces and system calls"
1078 #: build/C/man7/mq_overview.7:103
1080 "In most cases the B<mq_*>() library interfaces listed above are implemented "
1081 "on top of underlying system calls of the same name. Deviations from this "
1082 "scheme are indicated in the following table:"
1086 #: build/C/man7/mq_overview.7:107
1088 msgid "Library interface\tSystem call\n"
1092 #: build/C/man7/mq_overview.7:108
1094 msgid "mq_close(3)\tclose(2)\n"
1098 #: build/C/man7/mq_overview.7:109
1100 msgid "mq_getattr(3)\tmq_getsetattr(2)\n"
1104 #: build/C/man7/mq_overview.7:110
1106 msgid "mq_notify(3)\tmq_notify(2)\n"
1110 #: build/C/man7/mq_overview.7:111
1112 msgid "mq_open(3)\tmq_open(2)\n"
1116 #: build/C/man7/mq_overview.7:112
1118 msgid "mq_receive(3)\tmq_timedreceive(2)\n"
1122 #: build/C/man7/mq_overview.7:113
1124 msgid "mq_send(3)\tmq_timedsend(2)\n"
1128 #: build/C/man7/mq_overview.7:114
1130 msgid "mq_setattr(3)\tmq_getsetattr(2)\n"
1134 #: build/C/man7/mq_overview.7:115
1136 msgid "mq_timedreceive(3)\tmq_timedreceive(2)\n"
1140 #: build/C/man7/mq_overview.7:116
1142 msgid "mq_timedsend(3)\tmq_timedsend(2)\n"
1146 #: build/C/man7/mq_overview.7:117
1148 msgid "mq_unlink(3)\tmq_unlink(2)\n"
1152 #: build/C/man7/mq_overview.7:120
1158 #: build/C/man7/mq_overview.7:123
1160 "POSIX message queues have been supported on Linux since kernel 2.6.6. Glibc "
1161 "support has been provided since version 2.3.4."
1165 #: build/C/man7/mq_overview.7:123
1167 msgid "Kernel configuration"
1171 #: build/C/man7/mq_overview.7:128
1173 "Support for POSIX message queues is configurable via the "
1174 "B<CONFIG_POSIX_MQUEUE> kernel configuration option. This option is enabled "
1179 #: build/C/man7/mq_overview.7:128
1185 #: build/C/man7/mq_overview.7:133
1187 "POSIX message queues have kernel persistence: if not removed by "
1188 "B<mq_unlink>(3), a message queue will exist until the system is shut down."
1192 #: build/C/man7/mq_overview.7:133
1198 #: build/C/man7/mq_overview.7:138
1200 "Programs using the POSIX message queue API must be compiled with I<cc -lrt> "
1201 "to link against the real-time library, I<librt>."
1205 #: build/C/man7/mq_overview.7:138
1207 msgid "/proc interfaces"
1211 #: build/C/man7/mq_overview.7:141
1213 "The following interfaces can be used to limit the amount of kernel memory "
1214 "consumed by POSIX message queues:"
1218 #: build/C/man7/mq_overview.7:141
1220 msgid "I</proc/sys/fs/mqueue/msg_max>"
1224 #: build/C/man7/mq_overview.7:162
1226 "This file can be used to view and change the ceiling value for the maximum "
1227 "number of messages in a queue. This value acts as a ceiling on the "
1228 "I<attr-E<gt>mq_maxmsg> argument given to B<mq_open>(3). The default value "
1229 "for I<msg_max> is 10. The minimum value is 1 (10 in kernels before "
1230 "2.6.28). The upper limit is B<HARD_MAX>: I<(131072\\ /\\ sizeof(void\\ *))> "
1231 "(32768 on Linux/86). This limit is ignored for privileged processes "
1232 "(B<CAP_SYS_RESOURCE>), but the B<HARD_MAX> ceiling is nevertheless imposed."
1236 #: build/C/man7/mq_overview.7:162
1238 msgid "I</proc/sys/fs/mqueue/msgsize_max>"
1242 #: build/C/man7/mq_overview.7:181
1244 "This file can be used to view and change the ceiling on the maximum message "
1245 "size. This value acts as a ceiling on the I<attr-E<gt>mq_msgsize> argument "
1246 "given to B<mq_open>(3). The default value for I<msgsize_max> is 8192 "
1247 "bytes. The minimum value is 128 (8192 in kernels before 2.6.28). The upper "
1248 "limit for I<msgsize_max> is 1,048,576 (in kernels before 2.6.28, the upper "
1249 "limit was B<INT_MAX>; that is, 2,147,483,647 on Linux/86). This limit is "
1250 "ignored for privileged processes (B<CAP_SYS_RESOURCE>)."
1254 #: build/C/man7/mq_overview.7:181
1256 msgid "I</proc/sys/fs/mqueue/queues_max>"
1260 #: build/C/man7/mq_overview.7:191
1262 "This file can be used to view and change the system-wide limit on the number "
1263 "of message queues that can be created. Only privileged processes "
1264 "(B<CAP_SYS_RESOURCE>) can create new message queues once this limit has "
1265 "been reached. The default value for I<queues_max> is 256; it can be changed "
1266 "to any value in the range 0 to INT_MAX."
1270 #: build/C/man7/mq_overview.7:191
1272 msgid "Resource limit"
1276 #: build/C/man7/mq_overview.7:198
1278 "The B<RLIMIT_MSGQUEUE> resource limit, which places a limit on the amount of "
1279 "space that can be consumed by all of the message queues belonging to a "
1280 "process's real user ID, is described in B<getrlimit>(2)."
1284 #: build/C/man7/mq_overview.7:198
1286 msgid "Mounting the message queue filesystem"
1290 #: build/C/man7/mq_overview.7:204
1292 "On Linux, message queues are created in a virtual filesystem. (Other "
1293 "implementations may also provide such a feature, but the details are likely "
1294 "to differ.) This filesystem can be mounted (by the superuser) using the "
1295 "following commands:"
1299 #: build/C/man7/mq_overview.7:209
1302 "#B< mkdir /dev/mqueue>\n"
1303 "#B< mount -t mqueue none /dev/mqueue>\n"
1307 #: build/C/man7/mq_overview.7:213
1308 msgid "The sticky bit is automatically enabled on the mount directory."
1312 #: build/C/man7/mq_overview.7:220
1314 "After the filesystem has been mounted, the message queues on the system can "
1315 "be viewed and manipulated using the commands usually used for files (e.g., "
1316 "B<ls>(1) and B<rm>(1))."
1320 #: build/C/man7/mq_overview.7:223
1322 "The contents of each file in the directory consist of a single line "
1323 "containing information about the queue:"
1327 #: build/C/man7/mq_overview.7:228
1330 "$B< cat /dev/mqueue/mymq>\n"
1331 "QSIZE:129 NOTIFY:2 SIGNO:0 NOTIFY_PID:8260\n"
1335 #: build/C/man7/mq_overview.7:232
1336 msgid "These fields are as follows:"
1340 #: build/C/man7/mq_overview.7:232
1346 #: build/C/man7/mq_overview.7:235
1347 msgid "Number of bytes of data in all messages in the queue."
1351 #: build/C/man7/mq_overview.7:235
1353 msgid "B<NOTIFY_PID>"
1357 #: build/C/man7/mq_overview.7:241
1359 "If this is nonzero, then the process with this PID has used B<mq_notify>(3) "
1360 "to register for asynchronous message notification, and the remaining fields "
1361 "describe how notification occurs."
1365 #: build/C/man7/mq_overview.7:241
1371 #: build/C/man7/mq_overview.7:251
1373 "Notification method: 0 is B<SIGEV_SIGNAL>; 1 is B<SIGEV_NONE>; and 2 is "
1378 #: build/C/man7/mq_overview.7:251
1384 #: build/C/man7/mq_overview.7:255
1385 msgid "Signal number to be used for B<SIGEV_SIGNAL>."
1389 #: build/C/man7/mq_overview.7:255
1391 msgid "Polling message queue descriptors"
1395 #: build/C/man7/mq_overview.7:263
1397 "On Linux, a message queue descriptor is actually a file descriptor, and can "
1398 "be monitored using B<select>(2), B<poll>(2), or B<epoll>(7). This is not "
1403 #: build/C/man7/mq_overview.7:275
1405 "System V message queues (B<msgget>(2), B<msgsnd>(2), B<msgrcv>(2), etc.) are "
1406 "an older API for exchanging messages between processes. POSIX message "
1407 "queues provide a better designed interface than System V message queues; on "
1408 "the other hand POSIX message queues are less widely available (especially on "
1409 "older systems) than System V message queues."
1413 #: build/C/man7/mq_overview.7:278
1415 "Linux does not currently (2.6.26) support the use of access control lists "
1416 "(ACLs) for POSIX message queues."
1420 #: build/C/man7/mq_overview.7:281
1422 "An example of the use of various message queue functions is shown in "
1427 #: build/C/man7/mq_overview.7:294
1429 "B<getrlimit>(2), B<mq_getsetattr>(2), B<poll>(2), B<select>(2), "
1430 "B<mq_close>(3), B<mq_getattr>(3), B<mq_notify>(3), B<mq_open>(3), "
1431 "B<mq_receive>(3), B<mq_send>(3), B<mq_unlink>(3), B<epoll>(7)"
1435 #: build/C/man3/mq_receive.3:26
1441 #: build/C/man3/mq_receive.3:26 build/C/man3/mq_send.3:26
1447 #: build/C/man3/mq_receive.3:29
1448 msgid "mq_receive, mq_timedreceive - receive a message from a message queue"
1452 #: build/C/man3/mq_receive.3:35
1455 "B<ssize_t mq_receive(mqd_t >I<mqdes>B<, char *>I<msg_ptr>B<,>\n"
1456 "B< size_t >I<msg_len>B<, unsigned int *>I<msg_prio>B<);>\n"
1460 #: build/C/man3/mq_receive.3:38 build/C/man3/mq_send.3:38
1463 "B<#include E<lt>time.hE<gt>>\n"
1464 "B<#include E<lt>mqueue.hE<gt>>\n"
1468 #: build/C/man3/mq_receive.3:42
1471 "B<ssize_t mq_timedreceive(mqd_t >I<mqdes>B<, char *>I<msg_ptr>B<,>\n"
1472 "B< size_t >I<msg_len>B<, unsigned int *>I<msg_prio>B<,>\n"
1473 "B< const struct timespec *>I<abs_timeout>B<);>\n"
1477 #: build/C/man3/mq_receive.3:50 build/C/man3/mq_send.3:50
1478 msgid "Feature Test Macro Requirements for glibc (see B<feature_test_macros>(7)):"
1482 #: build/C/man3/mq_receive.3:53
1483 msgid "B<mq_timedreceive>():"
1487 #: build/C/man3/mq_receive.3:55 build/C/man3/mq_send.3:55
1488 msgid "_XOPEN_SOURCE\\ E<gt>=\\ 600 || _POSIX_C_SOURCE\\ E<gt>=\\ 200112L"
1492 #: build/C/man3/mq_receive.3:76
1494 "B<mq_receive>() removes the oldest message with the highest priority from "
1495 "the message queue referred to by the descriptor I<mqdes>, and places it in "
1496 "the buffer pointed to by I<msg_ptr>. The I<msg_len> argument specifies the "
1497 "size of the buffer pointed to by I<msg_ptr>; this must be greater than or "
1498 "equal to the I<mq_msgsize> attribute of the queue (see B<mq_getattr>(3)). "
1499 "If I<msg_prio> is not NULL, then the buffer to which it points is used to "
1500 "return the priority associated with the received message."
1504 #: build/C/man3/mq_receive.3:86
1506 "If the queue is empty, then, by default, B<mq_receive>() blocks until a "
1507 "message becomes available, or the call is interrupted by a signal handler. "
1508 "If the B<O_NONBLOCK> flag is enabled for the message queue description, then "
1509 "the call instead fails immediately with the error B<EAGAIN>."
1513 #: build/C/man3/mq_receive.3:99
1515 "B<mq_timedreceive>() behaves just like B<mq_receive>(), except that if the "
1516 "queue is empty and the B<O_NONBLOCK> flag is not enabled for the message "
1517 "queue description, then I<abs_timeout> points to a structure which specifies "
1518 "a ceiling on the time for which the call will block. This ceiling is an "
1519 "absolute timeout in seconds and nanoseconds since the Epoch, 1970-01-01 "
1520 "00:00:00 +0000 (UTC), and it is specified in the following structure:"
1524 #: build/C/man3/mq_receive.3:106 build/C/man3/mq_send.3:112
1527 "struct timespec {\n"
1528 " time_t tv_sec; /* seconds */\n"
1529 " long tv_nsec; /* nanoseconds */\n"
1534 #: build/C/man3/mq_receive.3:113
1536 "If no message is available, and the timeout has already expired by the time "
1537 "of the call, B<mq_timedreceive>() returns immediately."
1541 #: build/C/man3/mq_receive.3:122
1543 "On success, B<mq_receive>() and B<mq_timedreceive>() return the number of "
1544 "bytes in the received message; on error, -1 is returned, with I<errno> set "
1545 "to indicate the error."
1549 #: build/C/man3/mq_receive.3:123 build/C/man3/mq_send.3:128 build/C/man2/msgop.2:346 build/C/man2/msgop.2:401
1555 #: build/C/man3/mq_receive.3:129
1557 "The queue was empty, and the B<O_NONBLOCK> flag was set for the message "
1558 "queue description referred to by I<mqdes>."
1562 #: build/C/man3/mq_receive.3:134 build/C/man3/mq_send.3:139
1563 msgid "The descriptor specified in I<mqdes> was invalid."
1567 #: build/C/man3/mq_receive.3:134 build/C/man3/mq_send.3:139 build/C/man2/msgop.2:362 build/C/man2/msgop.2:416
1573 #: build/C/man3/mq_receive.3:138 build/C/man3/mq_send.3:143
1574 msgid "The call was interrupted by a signal handler; see B<signal>(7)."
1578 #: build/C/man3/mq_receive.3:147 build/C/man3/mq_send.3:152
1580 "The call would have blocked, and I<abs_timeout> was invalid, either because "
1581 "I<tv_sec> was less than zero, or because I<tv_nsec> was less than zero or "
1582 "greater than 1000 million."
1586 #: build/C/man3/mq_receive.3:147 build/C/man3/mq_send.3:152
1592 #: build/C/man3/mq_receive.3:153
1593 msgid "I<msg_len> was less than the I<mq_msgsize> attribute of the message queue."
1597 #: build/C/man3/mq_receive.3:153 build/C/man3/mq_send.3:158
1599 msgid "B<ETIMEDOUT>"
1603 #: build/C/man3/mq_receive.3:156 build/C/man3/mq_send.3:161
1604 msgid "The call timed out before a message could be transferred."
1608 #: build/C/man3/mq_receive.3:164
1610 "On Linux, B<mq_timedreceive>() is a system call, and B<mq_receive>() is a "
1611 "library function layered on top of that system call."
1615 #: build/C/man3/mq_receive.3:173
1617 "B<mq_close>(3), B<mq_getattr>(3), B<mq_notify>(3), B<mq_open>(3), "
1618 "B<mq_send>(3), B<mq_unlink>(3), B<mq_overview>(7), B<time>(7)"
1622 #: build/C/man3/mq_send.3:26
1628 #: build/C/man3/mq_send.3:29
1629 msgid "mq_send, mq_timedsend - send a message to a message queue"
1633 #: build/C/man3/mq_send.3:35
1636 "B<int mq_send(mqd_t >I<mqdes>B<, const char *>I<msg_ptr>B<,>\n"
1637 "B< size_t >I<msg_len>B<, unsigned int >I<msg_prio>B<);>\n"
1641 #: build/C/man3/mq_send.3:42
1644 "B<int mq_timedsend(mqd_t >I<mqdes>B<, const char *>I<msg_ptr>B<,>\n"
1645 "B< size_t >I<msg_len>B<, unsigned int >I<msg_prio>B<,>\n"
1646 "B< const struct timespec *>I<abs_timeout>B<);>\n"
1650 #: build/C/man3/mq_send.3:53
1651 msgid "B<mq_timedsend>():"
1655 #: build/C/man3/mq_send.3:71
1657 "B<mq_send>() adds the message pointed to by I<msg_ptr> to the message queue "
1658 "referred to by the descriptor I<mqdes>. The I<msg_len> argument specifies "
1659 "the length of the message pointed to by I<msg_ptr>; this length must be less "
1660 "than or equal to the queue's I<mq_msgsize> attribute. Zero-length messages "
1665 #: build/C/man3/mq_send.3:79
1667 "The I<msg_prio> argument is a nonnegative integer that specifies the "
1668 "priority of this message. Messages are placed on the queue in decreasing "
1669 "order of priority, with newer messages of the same priority being placed "
1670 "after older messages with the same priority."
1674 #: build/C/man3/mq_send.3:92
1676 "If the message queue is already full (i.e., the number of messages on the "
1677 "queue equals the queue's I<mq_maxmsg> attribute), then, by default, "
1678 "B<mq_send>() blocks until sufficient space becomes available to allow the "
1679 "message to be queued, or until the call is interrupted by a signal handler. "
1680 "If the B<O_NONBLOCK> flag is enabled for the message queue description, then "
1681 "the call instead fails immediately with the error B<EAGAIN>."
1685 #: build/C/man3/mq_send.3:105
1687 "B<mq_timedsend>() behaves just like B<mq_send>(), except that if the queue "
1688 "is full and the B<O_NONBLOCK> flag is not enabled for the message queue "
1689 "description, then I<abs_timeout> points to a structure which specifies a "
1690 "ceiling on the time for which the call will block. This ceiling is an "
1691 "absolute timeout in seconds and nanoseconds since the Epoch, 1970-01-01 "
1692 "00:00:00 +0000 (UTC), and it is specified in the following structure:"
1696 #: build/C/man3/mq_send.3:119
1698 "If the message queue is full, and the timeout has already expired by the "
1699 "time of the call, B<mq_timedsend>() returns immediately."
1703 #: build/C/man3/mq_send.3:127
1705 "On success, B<mq_send>() and B<mq_timedsend>() return zero; on error, -1 "
1706 "is returned, with I<errno> set to indicate the error."
1710 #: build/C/man3/mq_send.3:134
1712 "The queue was full, and the B<O_NONBLOCK> flag was set for the message queue "
1713 "description referred to by I<mqdes>."
1717 #: build/C/man3/mq_send.3:158
1719 "I<msg_len> was greater than the I<mq_msgsize> attribute of the message "
1724 #: build/C/man3/mq_send.3:169
1726 "On Linux, B<mq_timedsend>() is a system call, and B<mq_send>() is a "
1727 "library function layered on top of that system call."
1731 #: build/C/man3/mq_send.3:178
1733 "B<mq_close>(3), B<mq_getattr>(3), B<mq_notify>(3), B<mq_open>(3), "
1734 "B<mq_receive>(3), B<mq_unlink>(3), B<mq_overview>(7), B<time>(7)"
1738 #: build/C/man3/mq_unlink.3:26
1744 #: build/C/man3/mq_unlink.3:29
1745 msgid "mq_unlink - remove a message queue"
1749 #: build/C/man3/mq_unlink.3:34
1751 msgid "B<int mq_unlink(const char *>I<name>B<);>\n"
1755 #: build/C/man3/mq_unlink.3:44
1757 "B<mq_unlink>() removes the specified message queue I<name>. The message "
1758 "queue name is removed immediately. The queue itself is destroyed once any "
1759 "other processes that have the queue open close their descriptors referring "
1764 #: build/C/man3/mq_unlink.3:50
1766 "On success B<mq_unlink>() returns 0; on error, -1 is returned, with "
1767 "I<errno> set to indicate the error."
1771 #: build/C/man3/mq_unlink.3:54
1772 msgid "The caller does not have permission to unlink this message queue."
1776 #: build/C/man3/mq_unlink.3:62
1777 msgid "There is no message queue with the given I<name>."
1781 #: build/C/man3/mq_unlink.3:72
1783 "B<mq_close>(3), B<mq_getattr>(3), B<mq_notify>(3), B<mq_open>(3), "
1784 "B<mq_receive>(3), B<mq_send>(3), B<mq_overview>(7)"
1788 #: build/C/man2/msgctl.2:37
1794 #: build/C/man2/msgctl.2:37
1800 #: build/C/man2/msgctl.2:40
1801 msgid "msgctl - System V message control operations"
1805 #: build/C/man2/msgctl.2:45 build/C/man2/msgget.2:43 build/C/man2/msgop.2:48
1808 "B<#include E<lt>sys/types.hE<gt>>\n"
1809 "B<#include E<lt>sys/ipc.hE<gt>>\n"
1810 "B<#include E<lt>sys/msg.hE<gt>>\n"
1814 #: build/C/man2/msgctl.2:47
1816 msgid "B<int msgctl(int >I<msqid>B<, int >I<cmd>B<, struct msqid_ds *>I<buf>B<);>\n"
1820 #: build/C/man2/msgctl.2:54
1822 "B<msgctl>() performs the control operation specified by I<cmd> on the "
1823 "System V message queue with identifier I<msqid>."
1827 #: build/C/man2/msgctl.2:58
1829 "The I<msqid_ds> data structure is defined in I<E<lt>sys/msg.hE<gt>> as "
1834 #: build/C/man2/msgctl.2:75
1837 "struct msqid_ds {\n"
1838 " struct ipc_perm msg_perm; /* Ownership and permissions */\n"
1839 " time_t msg_stime; /* Time of last msgsnd(2) */\n"
1840 " time_t msg_rtime; /* Time of last msgrcv(2) */\n"
1841 " time_t msg_ctime; /* Time of last change */\n"
1842 " unsigned long __msg_cbytes; /* Current number of bytes in\n"
1843 " queue (nonstandard) */\n"
1844 " msgqnum_t msg_qnum; /* Current number of messages\n"
1846 " msglen_t msg_qbytes; /* Maximum number of bytes\n"
1847 " allowed in queue */\n"
1848 " pid_t msg_lspid; /* PID of last msgsnd(2) */\n"
1849 " pid_t msg_lrpid; /* PID of last msgrcv(2) */\n"
1854 #: build/C/man2/msgctl.2:83
1856 "The I<ipc_perm> structure is defined as follows (the highlighted fields are "
1857 "settable using B<IPC_SET>):"
1861 #: build/C/man2/msgctl.2:95
1864 "struct ipc_perm {\n"
1865 " key_t __key; /* Key supplied to msgget(2) */\n"
1866 " uid_t B<uid>; /* Effective UID of owner */\n"
1867 " gid_t B<gid>; /* Effective GID of owner */\n"
1868 " uid_t cuid; /* Effective UID of creator */\n"
1869 " gid_t cgid; /* Effective GID of creator */\n"
1870 " unsigned short B<mode>; /* Permissions */\n"
1871 " unsigned short __seq; /* Sequence number */\n"
1876 #: build/C/man2/msgctl.2:101
1877 msgid "Valid values for I<cmd> are:"
1881 #: build/C/man2/msgctl.2:101
1887 #: build/C/man2/msgctl.2:110
1889 "Copy information from the kernel data structure associated with I<msqid> "
1890 "into the I<msqid_ds> structure pointed to by I<buf>. The caller must have "
1891 "read permission on the message queue."
1895 #: build/C/man2/msgctl.2:110
1901 #: build/C/man2/msgctl.2:137
1903 "Write the values of some members of the I<msqid_ds> structure pointed to by "
1904 "I<buf> to the kernel data structure associated with this message queue, "
1905 "updating also its I<msg_ctime> member. The following members of the "
1906 "structure are updated: I<msg_qbytes>, I<msg_perm.uid>, I<msg_perm.gid>, and "
1907 "(the least significant 9 bits of) I<msg_perm.mode>. The effective UID of "
1908 "the calling process must match the owner (I<msg_perm.uid>) or creator "
1909 "(I<msg_perm.cuid>) of the message queue, or the caller must be privileged. "
1910 "Appropriate privilege (Linux: the B<CAP_SYS_RESOURCE> capability) is "
1911 "required to raise the I<msg_qbytes> value beyond the system parameter "
1916 #: build/C/man2/msgctl.2:137
1922 #: build/C/man2/msgctl.2:151
1924 "Immediately remove the message queue, awakening all waiting reader and "
1925 "writer processes (with an error return and I<errno> set to B<EIDRM>). The "
1926 "calling process must have appropriate privileges or its effective user ID "
1927 "must be either that of the creator or owner of the message queue. The third "
1928 "argument to B<msgctl>() is ignored in this case."
1932 #: build/C/man2/msgctl.2:151
1934 msgid "B<IPC_INFO> (Linux-specific)"
1938 #: build/C/man2/msgctl.2:164
1940 "Returns information about system-wide message queue limits and parameters in "
1941 "the structure pointed to by I<buf>. This structure is of type I<msginfo> "
1942 "(thus, a cast is required), defined in I<E<lt>sys/msg.hE<gt>> if the "
1943 "B<_GNU_SOURCE> feature test macro is defined:"
1947 #: build/C/man2/msgctl.2:188
1950 "struct msginfo {\n"
1951 " int msgpool; /* Size in kibibytes of buffer pool\n"
1952 " used to hold message data;\n"
1953 " unused within kernel */\n"
1954 " int msgmap; /* Maximum number of entries in message\n"
1955 " map; unused within kernel */\n"
1956 " int msgmax; /* Maximum number of bytes that can be\n"
1957 " written in a single message */\n"
1958 " int msgmnb; /* Maximum number of bytes that can be\n"
1959 " written to queue; used to initialize\n"
1960 " msg_qbytes during queue creation\n"
1962 " int msgmni; /* Maximum number of message queues */\n"
1963 " int msgssz; /* Message segment size;\n"
1964 " unused within kernel */\n"
1965 " int msgtql; /* Maximum number of messages on all queues\n"
1966 " in system; unused within kernel */\n"
1967 " unsigned short int msgseg;\n"
1968 " /* Maximum number of segments;\n"
1969 " unused within kernel */\n"
1974 #: build/C/man2/msgctl.2:201
1976 "The I<msgmni>, I<msgmax>, and I<msgmnb> settings can be changed via I</proc> "
1977 "files of the same name; see B<proc>(5) for details."
1981 #: build/C/man2/msgctl.2:201
1983 msgid "B<MSG_INFO> (Linux-specific)"
1987 #: build/C/man2/msgctl.2:218
1989 "Returns a I<msginfo> structure containing the same information as for "
1990 "B<IPC_INFO>, except that the following fields are returned with information "
1991 "about system resources consumed by message queues: the I<msgpool> field "
1992 "returns the number of message queues that currently exist on the system; the "
1993 "I<msgmap> field returns the total number of messages in all queues on the "
1994 "system; and the I<msgtql> field returns the total number of bytes in all "
1995 "messages in all queues on the system."
1999 #: build/C/man2/msgctl.2:218
2001 msgid "B<MSG_STAT> (Linux-specific)"
2005 #: build/C/man2/msgctl.2:229
2007 "Returns a I<msqid_ds> structure as for B<IPC_STAT>. However, the I<msqid> "
2008 "argument is not a queue identifier, but instead an index into the kernel's "
2009 "internal array that maintains information about all message queues on the "
2014 #: build/C/man2/msgctl.2:250
2016 "On success, B<IPC_STAT>, B<IPC_SET>, and B<IPC_RMID> return 0. A successful "
2017 "B<IPC_INFO> or B<MSG_INFO> operation returns the index of the highest used "
2018 "entry in the kernel's internal array recording information about all message "
2019 "queues. (This information can be used with repeated B<MSG_STAT> operations "
2020 "to obtain information about all queues on the system.) A successful "
2021 "B<MSG_STAT> operation returns the identifier of the queue whose index was "
2022 "given in I<msqid>."
2026 #: build/C/man2/msgctl.2:254
2027 msgid "On error, -1 is returned with I<errno> indicating the error."
2031 #: build/C/man2/msgctl.2:258
2032 msgid "On failure, I<errno> is set to one of the following:"
2036 #: build/C/man2/msgctl.2:271
2038 "The argument I<cmd> is equal to B<IPC_STAT> or B<MSG_STAT>, but the calling "
2039 "process does not have read permission on the message queue I<msqid>, and "
2040 "does not have the B<CAP_IPC_OWNER> capability."
2044 #: build/C/man2/msgctl.2:271 build/C/man2/msgop.2:354 build/C/man2/msgop.2:407
2050 #: build/C/man2/msgctl.2:282
2052 "The argument I<cmd> has the value B<IPC_SET> or B<IPC_STAT>, but the address "
2053 "pointed to by I<buf> isn't accessible."
2057 #: build/C/man2/msgctl.2:282 build/C/man2/msgop.2:359 build/C/man2/msgop.2:412
2063 #: build/C/man2/msgctl.2:285 build/C/man2/msgop.2:362
2064 msgid "The message queue was removed."
2068 #: build/C/man2/msgctl.2:296
2070 "Invalid value for I<cmd> or I<msqid>. Or: for a B<MSG_STAT> operation, the "
2071 "index value specified in I<msqid> referred to an array slot that is "
2076 #: build/C/man2/msgctl.2:296 build/C/man2/msgctl.2:314
2082 #: build/C/man2/msgctl.2:314
2084 "The argument I<cmd> has the value B<IPC_SET> or B<IPC_RMID>, but the "
2085 "effective user ID of the calling process is not the creator (as found in "
2086 "I<msg_perm.cuid>) or the owner (as found in I<msg_perm.uid>) of the "
2087 "message queue, and the caller is not privileged (Linux: does not have the "
2088 "B<CAP_SYS_ADMIN> capability)."
2092 #: build/C/man2/msgctl.2:325
2094 "An attempt (B<IPC_SET>) was made to increase I<msg_qbytes> beyond the "
2095 "system parameter B<MSGMNB>, but the caller is not privileged (Linux: does "
2096 "not have the B<CAP_SYS_RESOURCE> capability)."
2100 #: build/C/man2/msgctl.2:328 build/C/man2/msgget.2:185 build/C/man2/msgop.2:466
2101 msgid "SVr4, POSIX.1-2001."
2104 #. Like Linux, the FreeBSD man pages still document
2105 #. the inclusion of these header files.
2107 #: build/C/man2/msgctl.2:341 build/C/man2/msgget.2:198 build/C/man2/msgop.2:489
2109 "The inclusion of I<E<lt>sys/types.hE<gt>> and I<E<lt>sys/ipc.hE<gt>> isn't "
2110 "required on Linux or by any version of POSIX. However, some old "
2111 "implementations required the inclusion of these header files, and the SVID "
2112 "also documented their inclusion. Applications intended to be portable to "
2113 "such old systems may need to include these header files."
2117 #: build/C/man2/msgctl.2:353
2119 "The B<IPC_INFO>, B<MSG_STAT> and B<MSG_INFO> operations are used by the "
2120 "B<ipcs>(1) program to provide information on allocated resources. In the "
2121 "future these may modified or moved to a I</proc> filesystem interface."
2125 #: build/C/man2/msgctl.2:367
2127 "Various fields in the I<struct msqid_ds> were typed as I<short> under Linux "
2128 "2.2 and have become I<long> under Linux 2.4. To take advantage of this, a "
2129 "recompilation under glibc-2.1.91 or later should suffice. (The kernel "
2130 "distinguishes old and new calls by an B<IPC_64> flag in I<cmd>.)"
2134 #: build/C/man2/msgctl.2:374
2136 "B<msgget>(2), B<msgrcv>(2), B<msgsnd>(2), B<capabilities>(7), "
2137 "B<mq_overview>(7), B<svipc>(7)"
2141 #: build/C/man2/msgget.2:35
2147 #: build/C/man2/msgget.2:35
2153 #: build/C/man2/msgget.2:38
2154 msgid "msgget - get a System V message queue identifier"
2158 #: build/C/man2/msgget.2:45
2160 msgid "B<int msgget(key_t >I<key>B<, int >I<msgflg>B<);>\n"
2164 #: build/C/man2/msgget.2:67
2166 "The B<msgget>() system call returns the System V message queue identifier "
2167 "associated with the value of the I<key> argument. A new message queue is "
2168 "created if I<key> has the value B<IPC_PRIVATE> or I<key> isn't "
2169 "B<IPC_PRIVATE>, no message queue with the given key I<key> exists, and "
2170 "B<IPC_CREAT> is specified in I<msgflg>."
2174 #: build/C/man2/msgget.2:86
2176 "If I<msgflg> specifies both B<IPC_CREAT> and B<IPC_EXCL> and a message queue "
2177 "already exists for I<key>, then B<msgget>() fails with I<errno> set to "
2178 "B<EEXIST>. (This is analogous to the effect of the combination B<O_CREAT | "
2179 "O_EXCL> for B<open>(2).)"
2183 #: build/C/man2/msgget.2:96
2185 "Upon creation, the least significant bits of the argument I<msgflg> define "
2186 "the permissions of the message queue. These permission bits have the same "
2187 "format and semantics as the permissions specified for the I<mode> argument "
2188 "of B<open>(2). (The execute permissions are not used.)"
2192 #: build/C/man2/msgget.2:103
2194 "If a new message queue is created, then its associated data structure "
2195 "I<msqid_ds> (see B<msgctl>(2)) is initialized as follows:"
2199 #: build/C/man2/msgget.2:108
2201 "I<msg_perm.cuid> and I<msg_perm.uid> are set to the effective user ID of the "
2206 #: build/C/man2/msgget.2:113
2208 "I<msg_perm.cgid> and I<msg_perm.gid> are set to the effective group ID of "
2209 "the calling process."
2213 #: build/C/man2/msgget.2:118
2215 "The least significant 9 bits of I<msg_perm.mode> are set to the least "
2216 "significant 9 bits of I<msgflg>."
2220 #: build/C/man2/msgget.2:126
2222 "I<msg_qnum>, I<msg_lspid>, I<msg_lrpid>, I<msg_stime>, and I<msg_rtime> are "
2227 #: build/C/man2/msgget.2:129
2228 msgid "I<msg_ctime> is set to the current time."
2232 #: build/C/man2/msgget.2:133
2233 msgid "I<msg_qbytes> is set to the system limit B<MSGMNB>."
2237 #: build/C/man2/msgget.2:137
2239 "If the message queue already exists the permissions are verified, and a "
2240 "check is made to see if it is marked for destruction."
2244 #: build/C/man2/msgget.2:143
2246 "If successful, the return value will be the message queue identifier (a "
2247 "nonnegative integer), otherwise -1 with I<errno> indicating the error."
2251 #: build/C/man2/msgget.2:147
2252 msgid "On failure, I<errno> is set to one of the following values:"
2256 #: build/C/man2/msgget.2:155
2258 "A message queue exists for I<key>, but the calling process does not have "
2259 "permission to access the queue, and does not have the B<CAP_IPC_OWNER> "
2264 #: build/C/man2/msgget.2:165
2266 "A message queue exists for I<key> and I<msgflg> specified both B<IPC_CREAT> "
2271 #: build/C/man2/msgget.2:173
2273 "No message queue exists for I<key> and I<msgflg> did not specify "
2278 #: build/C/man2/msgget.2:177
2280 "A message queue has to be created but the system does not have enough memory "
2281 "for the new data structure."
2285 #: build/C/man2/msgget.2:183
2287 "A message queue has to be created but the system limit for the maximum "
2288 "number of message queues (B<MSGMNI>) would be exceeded."
2292 #: build/C/man2/msgget.2:208
2294 "B<IPC_PRIVATE> isn't a flag field but a I<key_t> type. If this special "
2295 "value is used for I<key>, the system call ignores everything but the least "
2296 "significant 9 bits of I<msgflg> and creates a new message queue (on "
2301 #: build/C/man2/msgget.2:212
2303 "The following is a system limit on message queue resources affecting a "
2308 #: build/C/man2/msgget.2:212
2314 #: build/C/man2/msgget.2:218
2316 "System wide maximum number of message queues: policy dependent (on Linux, "
2317 "this limit can be read and modified via I</proc/sys/kernel/msgmni>)."
2321 #: build/C/man2/msgget.2:218
2327 #: build/C/man2/msgget.2:224
2329 "Until version 2.3.20 Linux would return B<EIDRM> for a B<msgget>() on a "
2330 "message queue scheduled for deletion."
2334 #: build/C/man2/msgget.2:230
2336 "The name choice B<IPC_PRIVATE> was perhaps unfortunate, B<IPC_NEW> would "
2337 "more clearly show its function."
2341 #: build/C/man2/msgget.2:238
2343 "B<msgctl>(2), B<msgrcv>(2), B<msgsnd>(2), B<ftok>(3), B<capabilities>(7), "
2344 "B<mq_overview>(7), B<svipc>(7)"
2348 #: build/C/man2/msgop.2:40
2354 #: build/C/man2/msgop.2:40
2360 #: build/C/man2/msgop.2:43
2361 msgid "msgrcv, msgsnd - System V message queue operations"
2365 #: build/C/man2/msgop.2:51
2368 "B<int msgsnd(int >I<msqid>B<, const void *>I<msgp>B<, size_t >I<msgsz>B<, "
2369 "int >I<msgflg>B<);>\n"
2373 #: build/C/man2/msgop.2:55
2376 "B<ssize_t msgrcv(int >I<msqid>B<, void *>I<msgp>B<, size_t >I<msgsz>B<, long "
2378 "B< int >I<msgflg>B<);>\n"
2382 #: build/C/man2/msgop.2:65
2384 "The B<msgsnd>() and B<msgrcv>() system calls are used, respectively, to "
2385 "send messages to, and receive messages from, a System V message queue. The "
2386 "calling process must have write permission on the message queue in order to "
2387 "send a message, and read permission to receive a message."
2391 #: build/C/man2/msgop.2:70
2393 "The I<msgp> argument is a pointer to a caller-defined structure of the "
2394 "following general form:"
2398 #: build/C/man2/msgop.2:77
2402 " long mtype; /* message type, must be E<gt> 0 */\n"
2403 " char mtext[1]; /* message data */\n"
2408 #: build/C/man2/msgop.2:96
2410 "The I<mtext> field is an array (or other structure) whose size is specified "
2411 "by I<msgsz>, a nonnegative integer value. Messages of zero length (i.e., no "
2412 "I<mtext> field) are permitted. The I<mtype> field must have a strictly "
2413 "positive integer value. This value can be used by the receiving process for "
2414 "message selection (see the description of B<msgrcv>() below)."
2418 #: build/C/man2/msgop.2:96
2424 #: build/C/man2/msgop.2:104
2426 "The B<msgsnd>() system call appends a copy of the message pointed to by "
2427 "I<msgp> to the message queue whose identifier is specified by I<msqid>."
2431 #: build/C/man2/msgop.2:125
2433 "If sufficient space is available in the queue, B<msgsnd>() succeeds "
2434 "immediately. (The queue capacity is defined by the I<msg_qbytes> field in "
2435 "the associated data structure for the message queue. During queue creation "
2436 "this field is initialized to B<MSGMNB> bytes, but this limit can be modified "
2437 "using B<msgctl>(2).) If insufficient space is available in the queue, then "
2438 "the default behavior of B<msgsnd>() is to block until space becomes "
2439 "available. If B<IPC_NOWAIT> is specified in I<msgflg>, then the call "
2440 "instead fails with the error B<EAGAIN>."
2444 #: build/C/man2/msgop.2:129
2445 msgid "A blocked B<msgsnd>() call may also fail if:"
2449 #: build/C/man2/msgop.2:129 build/C/man2/msgop.2:136 build/C/man2/msgop.2:203 build/C/man2/msgop.2:208 build/C/man2/msgop.2:222 build/C/man2/msgop.2:290 build/C/man2/msgop.2:292 build/C/man2/msgop.2:298
2455 #: build/C/man2/msgop.2:136
2457 "the queue is removed, in which case the system call fails with I<errno> set "
2462 #: build/C/man2/msgop.2:148
2464 "a signal is caught, in which case the system call fails with I<errno> set to "
2465 "B<EINTR>;B<see> B<signal>(7). (B<msgsnd>() is never automatically "
2466 "restarted after being interrupted by a signal handler, regardless of the "
2467 "setting of the B<SA_RESTART> flag when establishing a signal handler.)"
2471 #: build/C/man2/msgop.2:151 build/C/man2/msgop.2:312
2473 "Upon successful completion the message queue data structure is updated as "
2478 #: build/C/man2/msgop.2:154
2479 msgid "I<msg_lspid> is set to the process ID of the calling process."
2483 #: build/C/man2/msgop.2:157
2484 msgid "I<msg_qnum> is incremented by 1."
2488 #: build/C/man2/msgop.2:160
2489 msgid "I<msg_stime> is set to the current time."
2493 #: build/C/man2/msgop.2:160
2499 #: build/C/man2/msgop.2:168
2501 "The B<msgrcv>() system call removes a message from the queue specified by "
2502 "I<msqid> and places it in the buffer pointed to by I<msgp>."
2506 #: build/C/man2/msgop.2:194
2508 "The argument I<msgsz> specifies the maximum size in bytes for the member "
2509 "I<mtext> of the structure pointed to by the I<msgp> argument. If the "
2510 "message text has length greater than I<msgsz>, then the behavior depends on "
2511 "whether B<MSG_NOERROR> is specified in I<msgflg>. If B<MSG_NOERROR> is "
2512 "specified, then the message text will be truncated (and the truncated part "
2513 "will be lost); if B<MSG_NOERROR> is not specified, then the message isn't "
2514 "removed from the queue and the system call fails returning -1 with I<errno> "
2519 #: build/C/man2/msgop.2:203
2521 "Unless B<MSG_COPY> is specified in I<msgflg> (see below), the I<msgtyp> "
2522 "argument specifies the type of message requested, as follows:"
2526 #: build/C/man2/msgop.2:208
2527 msgid "If I<msgtyp> is 0, then the first message in the queue is read."
2531 #: build/C/man2/msgop.2:222
2533 "If I<msgtyp> is greater than 0, then the first message in the queue of type "
2534 "I<msgtyp> is read, unless B<MSG_EXCEPT> was specified in I<msgflg>, in which "
2535 "case the first message in the queue of type not equal to I<msgtyp> will be "
2540 #: build/C/man2/msgop.2:230
2542 "If I<msgtyp> is less than 0, then the first message in the queue with the "
2543 "lowest type less than or equal to the absolute value of I<msgtyp> will be "
2548 #: build/C/man2/msgop.2:235
2550 "The I<msgflg> argument is a bit mask constructed by ORing together zero or "
2551 "more of the following flags:"
2555 #: build/C/man2/msgop.2:235
2557 msgid "B<IPC_NOWAIT>"
2561 #: build/C/man2/msgop.2:242
2563 "Return immediately if no message of the requested type is in the queue. The "
2564 "system call fails with I<errno> set to B<ENOMSG>."
2568 #: build/C/man2/msgop.2:242
2570 msgid "B<MSG_COPY> (since Linux 3.8)"
2573 #. commit 4a674f34ba04a002244edaf891b5da7fc1473ae8
2575 #: build/C/man2/msgop.2:249
2577 "Nondestructively fetch a copy of the message at the ordinal position in the "
2578 "queue specified by I<msgtyp> (messages are considered to be numbered "
2583 #: build/C/man2/msgop.2:263
2585 "This flag must be specified in conjunction with B<IPC_NOWAIT>, with the "
2586 "result that, if there is no message available at the given position, the "
2587 "call fails immediately with the error B<ENOMSG>. Because they alter the "
2588 "meaning of I<msgtyp> in orthogonal ways, B<MSG_COPY> and B<MSG_EXCEPT> may "
2589 "not both be specified in I<msgflg>."
2593 #: build/C/man2/msgop.2:271
2595 "The B<MSG_COPY> flag was added for the implementation of the kernel "
2596 "checkpoint-restore facility and is available only if the kernel was built "
2597 "with the B<CONFIG_CHECKPOINT_RESTORE> option."
2601 #: build/C/man2/msgop.2:271
2603 msgid "B<MSG_EXCEPT>"
2607 #: build/C/man2/msgop.2:279
2609 "Used with I<msgtyp> greater than 0 to read the first message in the queue "
2610 "with message type that differs from I<msgtyp>."
2614 #: build/C/man2/msgop.2:279
2616 msgid "B<MSG_NOERROR>"
2620 #: build/C/man2/msgop.2:284
2621 msgid "To truncate the message text if longer than I<msgsz> bytes."
2625 #: build/C/man2/msgop.2:290
2627 "If no message of the requested type is available and B<IPC_NOWAIT> isn't "
2628 "specified in I<msgflg>, the calling process is blocked until one of the "
2629 "following conditions occurs:"
2633 #: build/C/man2/msgop.2:292
2634 msgid "A message of the desired type is placed in the queue."
2638 #: build/C/man2/msgop.2:298
2640 "The message queue is removed from the system. In this case the system call "
2641 "fails with I<errno> set to B<EIDRM>."
2645 #: build/C/man2/msgop.2:309
2647 "The calling process catches a signal. In this case the system call fails "
2648 "with I<errno> set to B<EINTR>. (B<msgrcv>() is never automatically "
2649 "restarted after being interrupted by a signal handler, regardless of the "
2650 "setting of the B<SA_RESTART> flag when establishing a signal handler.)"
2654 #: build/C/man2/msgop.2:315
2655 msgid "I<msg_lrpid> is set to the process ID of the calling process."
2659 #: build/C/man2/msgop.2:318
2660 msgid "I<msg_qnum> is decremented by 1."
2664 #: build/C/man2/msgop.2:321
2665 msgid "I<msg_rtime> is set to the current time."
2669 #: build/C/man2/msgop.2:334
2671 "On failure both functions return -1 with I<errno> indicating the error, "
2672 "otherwise B<msgsnd>() returns 0 and B<msgrcv>() returns the number of "
2673 "bytes actually copied into the I<mtext> array."
2677 #: build/C/man2/msgop.2:340
2679 "When B<msgsnd>() fails, I<errno> will be set to one among the following "
2684 #: build/C/man2/msgop.2:346
2686 "The calling process does not have write permission on the message queue, and "
2687 "does not have the B<CAP_IPC_OWNER> capability."
2691 #: build/C/man2/msgop.2:354
2693 "The message can't be sent due to the I<msg_qbytes> limit for the queue and "
2694 "B<IPC_NOWAIT> was specified in I<msgflg>."
2698 #: build/C/man2/msgop.2:359 build/C/man2/msgop.2:412
2699 msgid "The address pointed to by I<msgp> isn't accessible."
2703 #: build/C/man2/msgop.2:365
2704 msgid "Sleeping on a full message queue condition, the process caught a signal."
2708 #: build/C/man2/msgop.2:376
2710 "Invalid I<msqid> value, or nonpositive I<mtype> value, or invalid I<msgsz> "
2711 "value (less than 0 or greater than the system value B<MSGMAX>)."
2715 #: build/C/man2/msgop.2:381
2717 "The system does not have enough memory to make a copy of the message pointed "
2722 #: build/C/man2/msgop.2:387
2724 "When B<msgrcv>() fails, I<errno> will be set to one among the following "
2729 #: build/C/man2/msgop.2:387
2735 #: build/C/man2/msgop.2:395
2737 "The message text length is greater than I<msgsz> and B<MSG_NOERROR> isn't "
2738 "specified in I<msgflg>."
2742 #: build/C/man2/msgop.2:401
2744 "The calling process does not have read permission on the message queue, and "
2745 "does not have the B<CAP_IPC_OWNER> capability."
2749 #: build/C/man2/msgop.2:407
2751 "No message was available in the queue and B<IPC_NOWAIT> was specified in "
2756 #: build/C/man2/msgop.2:416
2758 "While the process was sleeping to receive a message, the message queue was "
2763 #: build/C/man2/msgop.2:421
2765 "While the process was sleeping to receive a message, the process caught a "
2766 "signal; see B<signal>(7)."
2770 #: build/C/man2/msgop.2:427
2771 msgid "I<msgqid> was invalid, or I<msgsz> was less than 0."
2775 #: build/C/man2/msgop.2:427 build/C/man2/msgop.2:434
2777 msgid "B<EINVAL> (since Linux 3.14)"
2781 #: build/C/man2/msgop.2:434
2782 msgid "I<msgflg> specified B<MSG_COPY>, but not B<IPC_NOWAIT>."
2786 #: build/C/man2/msgop.2:441
2787 msgid "I<msgflg> specified both B<MSG_COPY> and B<MSG_EXCEPT>."
2791 #: build/C/man2/msgop.2:441 build/C/man2/msgop.2:447
2797 #: build/C/man2/msgop.2:447
2799 "B<IPC_NOWAIT> was specified in I<msgflg> and no message of the requested "
2800 "type existed on the message queue."
2804 #: build/C/man2/msgop.2:457
2806 "B<IPC_NOWAIT> and B<MSG_COPY> were specified in I<msgflg> and the queue "
2807 "contains less than I<msgtyp> messages."
2811 #: build/C/man2/msgop.2:457
2813 msgid "B<ENOSYS> (since Linux 3.8)"
2817 #: build/C/man2/msgop.2:464
2819 "I<MSG_COPY> was specified in I<msgflg>, and this kernel was configured "
2820 "without B<CONFIG_CHECKPOINT_RESTORE>."
2823 #. MSG_COPY since glibc 2.18
2825 #: build/C/man2/msgop.2:476
2827 "The B<MSG_EXCEPT> and B<MSG_COPY> flags are Linux-specific; their "
2828 "definitions can be obtained by defining the B<_GNU_SOURCE> feature test "
2833 #: build/C/man2/msgop.2:496
2835 "The I<msgp> argument is declared as I<struct msgbuf *> with libc4, libc5, "
2836 "glibc 2.0, glibc 2.1. It is declared as I<void *> with glibc 2.2 and later, "
2837 "as required by SUSv2 and SUSv3."
2841 #: build/C/man2/msgop.2:500
2843 "The following limits on message queue resources affect the B<msgsnd>() "
2848 #: build/C/man2/msgop.2:500
2854 #: build/C/man2/msgop.2:505
2856 "Maximum size for a message text: 8192 bytes (on Linux, this limit can be "
2857 "read and modified via I</proc/sys/kernel/msgmax>)."
2861 #: build/C/man2/msgop.2:505
2867 #: build/C/man2/msgop.2:515
2869 "Default maximum size in bytes of a message queue: 16384 bytes (on Linux, "
2870 "this limit can be read and modified via I</proc/sys/kernel/msgmnb>). The "
2871 "superuser can increase the size of a message queue beyond B<MSGMNB> by a "
2872 "B<msgctl>(2) system call."
2876 #: build/C/man2/msgop.2:521
2878 "The implementation has no intrinsic limits for the system wide maximum "
2879 "number of message headers (B<MSGTQL>) and for the system wide maximum size "
2880 "in bytes of the message pool (B<MSGPOOL>)."
2883 #. FIXME http://marc.info/?l=linux-kernel&m=139048542803605&w=2
2884 #. commit 4f87dac386cc43d5525da7a939d4b4e7edbea22c
2886 #: build/C/man2/msgop.2:541
2888 "In Linux 3.13 and earlier, if B<msgrcv>() was called with the B<MSG_COPY> "
2889 "flag, but without B<IPC_NOWAIT>, and the message queue contained less than "
2890 "I<msgtyp> messages, then the call would block until the next message is "
2891 "written to the queue. At that point, the call would return a copy of the "
2892 "message, I<regardless> of whether that message was at the ordinal position "
2893 "I<msgtyp>. This bug is fixed in Linux 3.14."
2896 #. FIXME http://marc.info/?l=linux-kernel&m=139048542803605&w=2
2897 #. commit 4f87dac386cc43d5525da7a939d4b4e7edbea22c
2899 #: build/C/man2/msgop.2:557
2901 "Specifying both B<MSG_COPY> and B<MSC_EXCEPT> in I<msgflg> is a logical "
2902 "error (since these flags impose different interpretations on I<msgtyp>). In "
2903 "Linux 3.13 and earlier, this error was not diagnosed by B<msgrcv>(). This "
2904 "bug is fixed in Linux 3.14."
2908 #: build/C/man2/msgop.2:563
2910 "B<msgctl>(2), B<msgget>(2), B<capabilities>(7), B<mq_overview>(7), "