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: 2012-05-01 04:38+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=CHARSET\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/man2/mq_getsetattr.2:26 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.2:35 build/C/man2/msgget.2:33 build/C/man2/msgop.2:38
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.2:35 build/C/man2/msgget.2:33 build/C/man2/msgop.2:38
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.2:36 build/C/man2/msgget.2:34 build/C/man2/msgop.2:39
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.2:38 build/C/man2/msgget.2:36 build/C/man2/msgop.2:41
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.2:37 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.2:46 build/C/man2/msgget.2:44 build/C/man2/msgop.2:54
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.2:224 build/C/man2/msgget.2:135 build/C/man2/msgop.2:285
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.2:249 build/C/man2/msgget.2:141 build/C/man2/msgop.2:298
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.2:47 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.2:309 build/C/man2/msgget.2:181 build/C/man2/msgop.2:397
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.2:49 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.2:312 build/C/man2/msgget.2:183 build/C/man2/msgop.2:399
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.2:53 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.2:337 build/C/man2/msgget.2:215 build/C/man2/msgop.2:431
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.2:56 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.2:344 build/C/man2/msgget.2:223 build/C/man2/msgop.2:437
170 #: build/C/man3/mq_close.3:80 build/C/man3/mq_getattr.3:162 build/C/man2/mq_getsetattr.2:63 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.2:351 build/C/man2/msgget.2:230 build/C/man2/msgop.2:444
172 "This page is part of release 3.40 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.2:280 build/C/man2/msgop.2:329 build/C/man2/msgop.2:385
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.2:29
308 msgid "mq_getsetattr - get/set message queue attributes"
312 #: build/C/man2/mq_getsetattr.2:33
315 "B<#include E<lt>sys/types.hE<gt>>\n"
316 "B<#include E<lt>mqueue.hE<gt>>\n"
320 #: build/C/man2/mq_getsetattr.2:36
323 "B<int mq_getsetattr(mqd_t >I<mqdes>B<, struct mq_attr *>I<newattr>B<,>\n"
324 "B< struct mq_attr *>I<oldattr>B<);>\n"
328 #: build/C/man2/mq_getsetattr.2:39
329 msgid "Do not use this system call."
333 #: build/C/man2/mq_getsetattr.2:47
335 "This is the low-level system call used to implement B<mq_getattr>(3) and "
336 "B<mq_setattr>(3). For an explanation of how this system call operates, see "
337 "the description of B<mq_setattr>(3)."
341 #: build/C/man2/mq_getsetattr.2:49
342 msgid "This interface is nonstandard; avoid its use."
346 #: build/C/man2/mq_getsetattr.2:53
348 "Glibc does not provide a wrapper for this system call; call it using "
349 "B<syscall>(2). (Actually, never call it unless you are writing a C "
354 #: build/C/man2/mq_getsetattr.2:56
355 msgid "B<mq_getattr>(3), B<mq_overview>(7)"
359 #: build/C/man3/mq_notify.3:26
365 #: build/C/man3/mq_notify.3:26
371 #: build/C/man3/mq_notify.3:29
372 msgid "mq_notify - register for notification when a message is available"
376 #: build/C/man3/mq_notify.3:34
378 msgid "B<int mq_notify(mqd_t >I<mqdes>B<, const struct sigevent *>I<sevp>B<);>\n"
382 #: build/C/man3/mq_notify.3:43
384 "B<mq_notify>() allows the calling process to register or unregister for "
385 "delivery of an asynchronous notification when a new message arrives on the "
386 "empty message queue referred to by the descriptor I<mqdes>."
390 #: build/C/man3/mq_notify.3:51
392 "The I<sevp> argument is a pointer to a I<sigevent> structure. For the "
393 "definition and general details of this structure, see B<sigevent>(7)."
397 #: build/C/man3/mq_notify.3:65
399 "If I<sevp> is a non-NULL pointer, then B<mq_notify>() registers the calling "
400 "process to receive message notification. The I<sigev_notify> field of the "
401 "I<sigevent> structure to which I<sevp> points specifies how notification is "
402 "to be performed. This field has one of the following values:"
406 #: build/C/man3/mq_notify.3:65
408 msgid "B<SIGEV_NONE>"
411 #. When is SIGEV_NONE useful?
413 #: build/C/man3/mq_notify.3:70
415 "A \"null\" notification: the calling process is registered as the target for "
416 "notification, but when a message arrives, no notification is sent."
420 #: build/C/man3/mq_notify.3:70
422 msgid "B<SIGEV_SIGNAL>"
425 #. I don't know of other implementations that set
426 #. si_pid and si_uid -- MTK
428 #: build/C/man3/mq_notify.3:90
430 "Notify the process by sending the signal specified in I<sigev_signo>. See "
431 "B<sigevent>(7) for general details. The I<si_code> field of the "
432 "I<siginfo_t> structure will be set to B<SI_MESGQ>. In addition, I<si_pid> "
433 "will be set to the PID of the process that sent the message, and I<si_uid> "
434 "will be set to the real user ID of the sending process."
438 #: build/C/man3/mq_notify.3:90
440 msgid "B<SIGEV_THREAD>"
444 #: build/C/man3/mq_notify.3:98
446 "Upon message delivery, invoke I<sigev_notify_function> as if it were the "
447 "start function of a new thread. See B<sigevent>(7) for details."
451 #: build/C/man3/mq_notify.3:101
453 "Only one process can be registered to receive notification from a message "
458 #: build/C/man3/mq_notify.3:108
460 "If I<sevp> is NULL, and the calling process is currently registered to "
461 "receive notifications for this message queue, then the registration is "
462 "removed; another process can then register to receive a message notification "
467 #: build/C/man3/mq_notify.3:115
469 "Message notification only occurs when a new message arrives and the queue "
470 "was previously empty. If the queue was not empty at the time B<mq_notify>() "
471 "was called, then a notification will only occur after the queue is emptied "
472 "and a new message arrives."
476 #: build/C/man3/mq_notify.3:123
478 "If another process or thread is waiting to read a message from an empty "
479 "queue using B<mq_receive>(3), then any message notification registration is "
480 "ignored: the message is delivered to the process or thread calling "
481 "B<mq_receive>(3), and the message notification registration remains in "
486 #: build/C/man3/mq_notify.3:134
488 "Notification occurs once: after a notification is delivered, the "
489 "notification registration is removed, and another process can register for "
490 "message notification. If the notified process wishes to receive the next "
491 "notification, it can use B<mq_notify>() to request a further notification. "
492 "This should be done before emptying all unread messages from the queue. "
493 "(Placing the queue in nonblocking mode is useful for emptying the queue of "
494 "messages without blocking once it is empty.)"
498 #: build/C/man3/mq_notify.3:140
500 "On success B<mq_notify>() returns 0; on error, -1 is returned, with "
501 "I<errno> set to indicate the error."
505 #: build/C/man3/mq_notify.3:146
511 #: build/C/man3/mq_notify.3:150
513 "Another process has already registered to receive notification for this "
518 #: build/C/man3/mq_notify.3:160
520 "I<sevp-E<gt>sigev_notify> is not one of the permitted values; or "
521 "I<sevp-E<gt>sigev_notify> is B<SIGEV_SIGNAL> and I<sevp-E<gt>sigev_signo> is "
522 "not a valid signal number."
526 #: build/C/man3/mq_notify.3:160 build/C/man3/mq_open.3:214 build/C/man2/msgget.2:171 build/C/man2/msgop.2:340
532 #: build/C/man3/mq_notify.3:163 build/C/man3/mq_open.3:217
533 msgid "Insufficient memory."
536 #. Linux does not do this
538 #: build/C/man3/mq_notify.3:174
540 "POSIX.1-2008 says that an implementation I<may> generate an B<EINVAL> error "
541 "if I<sevp> is NULL, and the caller is not currently registered to receive "
542 "notifications for the queue I<mqdes>."
546 #: build/C/man3/mq_notify.3:176 build/C/man7/mq_overview.7:278
552 #: build/C/man3/mq_notify.3:182
554 "The following program registers a notification request for the message queue "
555 "named in its command-line argument. Notification is performed by creating a "
556 "thread. The thread executes a function which reads one message from the "
557 "queue and then terminates the process."
561 #: build/C/man3/mq_notify.3:189
564 "#include E<lt>pthread.hE<gt>\n"
565 "#include E<lt>mqueue.hE<gt>\n"
566 "#include E<lt>stdio.hE<gt>\n"
567 "#include E<lt>stdlib.hE<gt>\n"
568 "#include E<lt>unistd.hE<gt>\n"
572 #: build/C/man3/mq_notify.3:192
575 "#define handle_error(msg) \\e\n"
576 " do { perror(msg); exit(EXIT_FAILURE); } while (0)\n"
580 #: build/C/man3/mq_notify.3:200
583 "static void /* Thread start function */\n"
584 "tfunc(union sigval sv)\n"
586 " struct mq_attr attr;\n"
589 " mqd_t mqdes = *((mqd_t *) sv.sival_ptr);\n"
593 #: build/C/man3/mq_notify.3:202
595 msgid " /* Determine max. msg size; allocate buffer to receive msg */\n"
599 #: build/C/man3/mq_notify.3:208
602 " if (mq_getattr(mqdes, &attr) == -1)\n"
603 " handle_error(\"mq_getattr\");\n"
604 " buf = malloc(attr.mq_msgsize);\n"
605 " if (buf == NULL)\n"
606 " handle_error(\"malloc\");\n"
610 #: build/C/man3/mq_notify.3:212
613 " nr = mq_receive(mqdes, buf, attr.mq_msgsize, NULL);\n"
615 " handle_error(\"mq_receive\");\n"
619 #: build/C/man3/mq_notify.3:217
622 " printf(\"Read %ld bytes from MQ\\en\", (long) nr);\n"
624 " exit(EXIT_SUCCESS); /* Terminate the process */\n"
629 #: build/C/man3/mq_notify.3:223
633 "main(int argc, char *argv[])\n"
636 " struct sigevent sev;\n"
640 #: build/C/man3/mq_notify.3:228
643 " if (argc != 2) {\n"
644 "\tfprintf(stderr, \"Usage: %s E<lt>mq-nameE<gt>\\en\", argv[0]);\n"
645 "\texit(EXIT_FAILURE);\n"
650 #: build/C/man3/mq_notify.3:232
653 " mqdes = mq_open(argv[1], O_RDONLY);\n"
654 " if (mqdes == (mqd_t) -1)\n"
655 " handle_error(\"mq_open\");\n"
659 #: build/C/man3/mq_notify.3:239
662 " sev.sigev_notify = SIGEV_THREAD;\n"
663 " sev.sigev_notify_function = tfunc;\n"
664 " sev.sigev_notify_attributes = NULL;\n"
665 " sev.sigev_value.sival_ptr = &mqdes; /* Arg. to thread func. */\n"
666 " if (mq_notify(mqdes, &sev) == -1)\n"
667 " handle_error(\"mq_notify\");\n"
671 #: build/C/man3/mq_notify.3:242
674 " pause(); /* Process will be terminated by thread function */\n"
679 #: build/C/man3/mq_notify.3:252
681 "B<mq_close>(3), B<mq_getattr>(3), B<mq_open>(3), B<mq_receive>(3), "
682 "B<mq_send>(3), B<mq_unlink>(3), B<mq_overview>(7), B<sigevent>(7)"
686 #: build/C/man3/mq_open.3:26
692 #: build/C/man3/mq_open.3:26
698 #: build/C/man3/mq_open.3:29
699 msgid "mq_open - open a message queue"
703 #: build/C/man3/mq_open.3:34
706 "B<#include E<lt>fcntl.hE<gt>> /* For O_* constants */\n"
707 "B<#include E<lt>sys/stat.hE<gt>> /* For mode constants */\n"
708 "B<#include E<lt>mqueue.hE<gt>>\n"
712 #: build/C/man3/mq_open.3:38
715 "B<mqd_t mq_open(const char *>I<name>B<, int >I<oflag>B<);>\n"
716 "B<mqd_t mq_open(const char *>I<name>B<, int >I<oflag>B<, mode_t "
718 "B< struct mq_attr *>I<attr>B<);>\n"
722 #: build/C/man3/mq_open.3:50
724 "B<mq_open>() creates a new POSIX message queue or opens an existing queue. "
725 "The queue is identified by I<name>. For details of the construction of "
726 "I<name>, see B<mq_overview>(7)."
730 #: build/C/man3/mq_open.3:58
732 "The I<oflag> argument specifies flags that control the operation of the "
733 "call. (Definitions of the flags values can be obtained by including "
734 "I<E<lt>fcntl.hE<gt>>.) Exactly one of the following must be specified in "
739 #: build/C/man3/mq_open.3:58
745 #: build/C/man3/mq_open.3:61
746 msgid "Open the queue to receive messages only."
750 #: build/C/man3/mq_open.3:61
756 #: build/C/man3/mq_open.3:64
757 msgid "Open the queue to send messages only."
761 #: build/C/man3/mq_open.3:64
767 #: build/C/man3/mq_open.3:67
768 msgid "Open the queue to both send and receive messages."
772 #: build/C/man3/mq_open.3:72
773 msgid "Zero or more of the following flags can additionally be I<OR>ed in I<oflag>:"
777 #: build/C/man3/mq_open.3:72
779 msgid "B<O_NONBLOCK>"
783 #: build/C/man3/mq_open.3:81
785 "Open the queue in nonblocking mode. In circumstances where B<mq_receive>(3) "
786 "and B<mq_send>(3) would normally block, these functions instead fail with "
787 "the error B<EAGAIN>."
791 #: build/C/man3/mq_open.3:81
796 #. In reality the file system IDs are used on Linux.
798 #: build/C/man3/mq_open.3:89
800 "Create the message queue if it does not exist. The owner (user ID) of the "
801 "message queue is set to the effective user ID of the calling process. The "
802 "group ownership (group ID) is set to the effective group ID of the calling "
807 #: build/C/man3/mq_open.3:89
813 #: build/C/man3/mq_open.3:99
815 "If B<O_CREAT> was specified in I<oflag>, and a queue with the given I<name> "
816 "already exists, then fail with the error B<EEXIST>."
820 #: build/C/man3/mq_open.3:123
822 "If B<O_CREAT> is specified in I<oflag>, then two additional arguments must "
823 "be supplied. The I<mode> argument specifies the permissions to be placed on "
824 "the new queue, as for B<open>(2). (Symbolic definitions for the permissions "
825 "bits can be obtained by including I<E<lt>sys/stat.hE<gt>>.) The permissions "
826 "settings are masked against the process umask. The I<attr> argument "
827 "specifies attributes for the queue. See B<mq_getattr>(3) for details. If "
828 "I<attr> is NULL, then the queue is created with implementation-defined "
829 "default attributes."
833 #: build/C/man3/mq_open.3:135
835 "On success, B<mq_open>() returns a message queue descriptor for use by "
836 "other message queue functions. On error, B<mq_open>() returns I<(mqd_t)\\ "
837 "-1>, with I<errno> set to indicate the error."
841 #: 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.2:253 build/C/man2/msgget.2:145 build/C/man2/msgop.2:304 build/C/man2/msgop.2:359
847 #: build/C/man3/mq_open.3:140
849 "The queue exists, but the caller does not have permission to open it in the "
853 #. Note that this isn't consistent with the same case for sem_open()
855 #: build/C/man3/mq_open.3:145
856 msgid "I<name> contained more than one slash."
860 #: build/C/man3/mq_open.3:145 build/C/man2/msgget.2:153
866 #: build/C/man3/mq_open.3:156
868 "Both B<O_CREAT> and B<O_EXCL> were specified in I<oflag>, but a queue with "
869 "this I<name> already exists."
873 #: build/C/man3/mq_open.3:188
875 "B<O_CREAT> was specified in I<oflag>, and I<attr> was not NULL, but "
876 "I<attr-E<gt>mq_maxmsg> or I<attr-E<gt>mq_msqsize> was invalid. Both of "
877 "these fields must be greater than zero. In a process that is unprivileged "
878 "(does not have the B<CAP_SYS_RESOURCE> capability), I<attr-E<gt>mq_maxmsg> "
879 "must be less than or equal to the I<msg_max> limit, and "
880 "I<attr-E<gt>mq_msgsize> must be less than or equal to the I<msgsize_max> "
881 "limit. In addition, even in a privileged process, I<attr-E<gt>mq_maxmsg> "
882 "cannot exceed the B<HARD_MAX> limit. (See B<mq_overview>(7) for details of "
887 #: build/C/man3/mq_open.3:188
893 #: build/C/man3/mq_open.3:192
894 msgid "The process already has the maximum number of files and message queues open."
898 #: build/C/man3/mq_open.3:192 build/C/man3/mq_unlink.3:54
900 msgid "B<ENAMETOOLONG>"
904 #: build/C/man3/mq_open.3:196 build/C/man3/mq_unlink.3:58
905 msgid "I<name> was too long."
909 #: build/C/man3/mq_open.3:196
915 #: build/C/man3/mq_open.3:200
917 "The system limit on the total number of open files and message queues has "
922 #: 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.2:163
928 #: build/C/man3/mq_open.3:209
930 "The B<O_CREAT> flag was not specified in I<oflag>, and no queue with this "
934 #. Note that this isn't consistent with the same case for sem_open()
936 #: build/C/man3/mq_open.3:214
937 msgid "I<name> was just \"/\" followed by no other characters."
941 #: build/C/man3/mq_open.3:217 build/C/man2/msgget.2:175
947 #: build/C/man3/mq_open.3:224
949 "Insufficient space for the creation of a new message queue. This probably "
950 "occurred because the I<queues_max> limit was encountered; see "
955 #: build/C/man3/mq_open.3:226 build/C/man2/msgget.2:209
961 #: build/C/man3/mq_open.3:230
963 "In kernels before 2.6.14, the process umask was not applied to the "
964 "permissions specified in I<mode>."
968 #: build/C/man3/mq_open.3:238
970 "B<mq_close>(3), B<mq_getattr>(3), B<mq_notify>(3), B<mq_receive>(3), "
971 "B<mq_send>(3), B<mq_unlink>(3), B<mq_overview>(7)"
975 #: build/C/man7/mq_overview.7:26
981 #: build/C/man7/mq_overview.7:26
987 #: build/C/man7/mq_overview.7:29
988 msgid "mq_overview - Overview of POSIX message queues"
992 #: build/C/man7/mq_overview.7:37
994 "POSIX message queues allow processes to exchange data in the form of "
995 "messages. This API is distinct from that provided by System V message "
996 "queues (B<msgget>(2), B<msgsnd>(2), B<msgrcv>(2), etc.), but provides "
997 "similar functionality."
1001 #: build/C/man7/mq_overview.7:52
1003 "Message queues are created and opened using B<mq_open>(3); this function "
1004 "returns a I<message queue descriptor> (I<mqd_t>), which is used to refer to "
1005 "the open message queue in later calls. Each message queue is identified by "
1006 "a name of the form I</somename>; that is, a null-terminated string of up to "
1007 "B<NAME_MAX> (i.e., 255) characters consisting of an initial slash, followed "
1008 "by one or more characters, none of which are slashes. Two processes can "
1009 "operate on the same queue by passing the same name to B<mq_open>(3)."
1013 #: build/C/man7/mq_overview.7:68
1015 "Messages are transferred to and from a queue using B<mq_send>(3) and "
1016 "B<mq_receive>(3). When a process has finished using the queue, it closes it "
1017 "using B<mq_close>(3), and when the queue is no longer required, it can be "
1018 "deleted using B<mq_unlink>(3). Queue attributes can be retrieved and (in "
1019 "some cases) modified using B<mq_getattr>(3) and B<mq_setattr>(3). A "
1020 "process can request asynchronous notification of the arrival of a message on "
1021 "a previously empty queue using B<mq_notify>(3)."
1025 #: build/C/man7/mq_overview.7:81
1027 "A message queue descriptor is a reference to an I<open message queue "
1028 "description> (cf. B<open>(2)). After a B<fork>(2), a child inherits copies "
1029 "of its parent's message queue descriptors, and these descriptors refer to "
1030 "the same open message queue descriptions as the corresponding descriptors in "
1031 "the parent. Corresponding descriptors in the two processes share the flags "
1032 "(I<mq_flags>) that are associated with the open message queue description."
1036 #: build/C/man7/mq_overview.7:94
1038 "Each message has an associated I<priority>, and messages are always "
1039 "delivered to the receiving process highest priority first. Message "
1040 "priorities range from 0 (low) to I<sysconf(_SC_MQ_PRIO_MAX)\\ -\\ 1> "
1041 "(high). On Linux, I<sysconf(_SC_MQ_PRIO_MAX)> returns 32768, but "
1042 "POSIX.1-2001 only requires an implementation to support priorities in the "
1043 "range 0 to 31; some implementations only provide this range."
1047 #: build/C/man7/mq_overview.7:97
1049 "The remainder of this section describes some specific details of the Linux "
1050 "implementation of POSIX message queues."
1054 #: build/C/man7/mq_overview.7:97
1056 msgid "Library interfaces and system calls"
1060 #: build/C/man7/mq_overview.7:103
1062 "In most cases the B<mq_*()> library interfaces listed above are implemented "
1063 "on top of underlying system calls of the same name. Deviations from this "
1064 "scheme are indicated in the following table:"
1068 #: build/C/man7/mq_overview.7:107
1070 msgid "Library interface\tSystem call\n"
1074 #: build/C/man7/mq_overview.7:108
1076 msgid "mq_close(3)\tclose(2)\n"
1080 #: build/C/man7/mq_overview.7:109
1082 msgid "mq_getattr(3)\tmq_getsetattr(2)\n"
1086 #: build/C/man7/mq_overview.7:110
1088 msgid "mq_notify(3)\tmq_notify(2)\n"
1092 #: build/C/man7/mq_overview.7:111
1094 msgid "mq_open(3)\tmq_open(2)\n"
1098 #: build/C/man7/mq_overview.7:112
1100 msgid "mq_receive(3)\tmq_timedreceive(2)\n"
1104 #: build/C/man7/mq_overview.7:113
1106 msgid "mq_send(3)\tmq_timedsend(2)\n"
1110 #: build/C/man7/mq_overview.7:114
1112 msgid "mq_setattr(3)\tmq_getsetattr(2)\n"
1116 #: build/C/man7/mq_overview.7:115
1118 msgid "mq_timedreceive(3)\tmq_timedreceive(2)\n"
1122 #: build/C/man7/mq_overview.7:116
1124 msgid "mq_timedsend(3)\tmq_timedsend(2)\n"
1128 #: build/C/man7/mq_overview.7:117
1130 msgid "mq_unlink(3)\tmq_unlink(2)\n"
1134 #: build/C/man7/mq_overview.7:120
1140 #: build/C/man7/mq_overview.7:123
1142 "POSIX message queues have been supported on Linux since kernel 2.6.6. Glibc "
1143 "support has been provided since version 2.3.4."
1147 #: build/C/man7/mq_overview.7:123
1149 msgid "Kernel configuration"
1153 #: build/C/man7/mq_overview.7:128
1155 "Support for POSIX message queues is configurable via the "
1156 "B<CONFIG_POSIX_MQUEUE> kernel configuration option. This option is enabled "
1161 #: build/C/man7/mq_overview.7:128
1167 #: build/C/man7/mq_overview.7:133
1169 "POSIX message queues have kernel persistence: if not removed by "
1170 "B<mq_unlink>(3), a message queue will exist until the system is shut down."
1174 #: build/C/man7/mq_overview.7:133
1180 #: build/C/man7/mq_overview.7:138
1182 "Programs using the POSIX message queue API must be compiled with I<cc -lrt> "
1183 "to link against the real-time library, I<librt>."
1187 #: build/C/man7/mq_overview.7:138
1189 msgid "/proc interfaces"
1193 #: build/C/man7/mq_overview.7:141
1195 "The following interfaces can be used to limit the amount of kernel memory "
1196 "consumed by POSIX message queues:"
1200 #: build/C/man7/mq_overview.7:141
1202 msgid "I</proc/sys/fs/mqueue/msg_max>"
1206 #: build/C/man7/mq_overview.7:162
1208 "This file can be used to view and change the ceiling value for the maximum "
1209 "number of messages in a queue. This value acts as a ceiling on the "
1210 "I<attr-E<gt>mq_maxmsg> argument given to B<mq_open>(3). The default value "
1211 "for I<msg_max> is 10. The minimum value is 1 (10 in kernels before "
1212 "2.6.28). The upper limit is B<HARD_MAX>: I<(131072\\ /\\ sizeof(void\\ *))> "
1213 "(32768 on Linux/86). This limit is ignored for privileged processes "
1214 "(B<CAP_SYS_RESOURCE>), but the B<HARD_MAX> ceiling is nevertheless imposed."
1218 #: build/C/man7/mq_overview.7:162
1220 msgid "I</proc/sys/fs/mqueue/msgsize_max>"
1224 #: build/C/man7/mq_overview.7:181
1226 "This file can be used to view and change the ceiling on the maximum message "
1227 "size. This value acts as a ceiling on the I<attr-E<gt>mq_msgsize> argument "
1228 "given to B<mq_open>(3). The default value for I<msgsize_max> is 8192 "
1229 "bytes. The minimum value is 128 (8192 in kernels before 2.6.28). The upper "
1230 "limit for I<msgsize_max> is 1,048,576 (in kernels before 2.6.28, the upper "
1231 "limit was B<INT_MAX>; that is, 2,147,483,647 on Linux/86). This limit is "
1232 "ignored for privileged processes (B<CAP_SYS_RESOURCE>)."
1236 #: build/C/man7/mq_overview.7:181
1238 msgid "I</proc/sys/fs/mqueue/queues_max>"
1242 #: build/C/man7/mq_overview.7:191
1244 "This file can be used to view and change the system-wide limit on the number "
1245 "of message queues that can be created. Only privileged processes "
1246 "(B<CAP_SYS_RESOURCE>) can create new message queues once this limit has "
1247 "been reached. The default value for I<queues_max> is 256; it can be changed "
1248 "to any value in the range 0 to INT_MAX."
1252 #: build/C/man7/mq_overview.7:191
1254 msgid "Resource limit"
1258 #: build/C/man7/mq_overview.7:198
1260 "The B<RLIMIT_MSGQUEUE> resource limit, which places a limit on the amount of "
1261 "space that can be consumed by all of the message queues belonging to a "
1262 "process's real user ID, is described in B<getrlimit>(2)."
1266 #: build/C/man7/mq_overview.7:198
1268 msgid "Mounting the message queue file system"
1272 #: build/C/man7/mq_overview.7:204
1274 "On Linux, message queues are created in a virtual file system. (Other "
1275 "implementations may also provide such a feature, but the details are likely "
1276 "to differ.) This file system can be mounted (by the superuser) using the "
1277 "following commands:"
1281 #: build/C/man7/mq_overview.7:209
1284 "#B< mkdir /dev/mqueue>\n"
1285 "#B< mount -t mqueue none /dev/mqueue>\n"
1289 #: build/C/man7/mq_overview.7:213
1290 msgid "The sticky bit is automatically enabled on the mount directory."
1294 #: build/C/man7/mq_overview.7:220
1296 "After the file system has been mounted, the message queues on the system can "
1297 "be viewed and manipulated using the commands usually used for files (e.g., "
1298 "B<ls>(1) and B<rm>(1))."
1302 #: build/C/man7/mq_overview.7:223
1304 "The contents of each file in the directory consist of a single line "
1305 "containing information about the queue:"
1309 #: build/C/man7/mq_overview.7:228
1312 "$B< cat /dev/mqueue/mymq>\n"
1313 "QSIZE:129 NOTIFY:2 SIGNO:0 NOTIFY_PID:8260\n"
1317 #: build/C/man7/mq_overview.7:232
1318 msgid "These fields are as follows:"
1322 #: build/C/man7/mq_overview.7:232
1328 #: build/C/man7/mq_overview.7:235
1329 msgid "Number of bytes of data in all messages in the queue."
1333 #: build/C/man7/mq_overview.7:235
1335 msgid "B<NOTIFY_PID>"
1339 #: build/C/man7/mq_overview.7:241
1341 "If this is nonzero, then the process with this PID has used B<mq_notify>(3) "
1342 "to register for asynchronous message notification, and the remaining fields "
1343 "describe how notification occurs."
1347 #: build/C/man7/mq_overview.7:241
1353 #: build/C/man7/mq_overview.7:251
1355 "Notification method: 0 is B<SIGEV_SIGNAL>; 1 is B<SIGEV_NONE>; and 2 is "
1360 #: build/C/man7/mq_overview.7:251
1366 #: build/C/man7/mq_overview.7:255
1367 msgid "Signal number to be used for B<SIGEV_SIGNAL>."
1371 #: build/C/man7/mq_overview.7:255
1373 msgid "Polling message queue descriptors"
1377 #: build/C/man7/mq_overview.7:263
1379 "On Linux, a message queue descriptor is actually a file descriptor, and can "
1380 "be monitored using B<select>(2), B<poll>(2), or B<epoll>(7). This is not "
1385 #: build/C/man7/mq_overview.7:275
1387 "System V message queues (B<msgget>(2), B<msgsnd>(2), B<msgrcv>(2), etc.) are "
1388 "an older API for exchanging messages between processes. POSIX message "
1389 "queues provide a better designed interface than System V message queues; on "
1390 "the other hand POSIX message queues are less widely available (especially on "
1391 "older systems) than System V message queues."
1395 #: build/C/man7/mq_overview.7:278
1397 "Linux does not currently (2.6.26) support the use of access control lists "
1398 "(ACLs) for POSIX message queues."
1402 #: build/C/man7/mq_overview.7:281
1404 "An example of the use of various message queue functions is shown in "
1409 #: build/C/man7/mq_overview.7:294
1411 "B<getrlimit>(2), B<mq_getsetattr>(2), B<poll>(2), B<select>(2), "
1412 "B<mq_close>(3), B<mq_getattr>(3), B<mq_notify>(3), B<mq_open>(3), "
1413 "B<mq_receive>(3), B<mq_send>(3), B<mq_unlink>(3), B<epoll>(7)"
1417 #: build/C/man3/mq_receive.3:26
1423 #: build/C/man3/mq_receive.3:26 build/C/man3/mq_send.3:26
1429 #: build/C/man3/mq_receive.3:29
1430 msgid "mq_receive, mq_timedreceive - receive a message from a message queue"
1434 #: build/C/man3/mq_receive.3:35
1437 "B<ssize_t mq_receive(mqd_t >I<mqdes>B<, char *>I<msg_ptr>B<,>\n"
1438 "B< size_t >I<msg_len>B<, unsigned *>I<msg_prio>B<);>\n"
1442 #: build/C/man3/mq_receive.3:38 build/C/man3/mq_send.3:38
1445 "B<#include E<lt>time.hE<gt>>\n"
1446 "B<#include E<lt>mqueue.hE<gt>>\n"
1450 #: build/C/man3/mq_receive.3:42
1453 "B<ssize_t mq_timedreceive(mqd_t >I<mqdes>B<, char *>I<msg_ptr>B<,>\n"
1454 "B< size_t >I<msg_len>B<, unsigned *>I<msg_prio>B<,>\n"
1455 "B< const struct timespec *>I<abs_timeout>B<);>\n"
1459 #: build/C/man3/mq_receive.3:50 build/C/man3/mq_send.3:50
1460 msgid "Feature Test Macro Requirements for glibc (see B<feature_test_macros>(7)):"
1464 #: build/C/man3/mq_receive.3:53
1465 msgid "B<mq_timedreceive>():"
1469 #: build/C/man3/mq_receive.3:55 build/C/man3/mq_send.3:55
1470 msgid "_XOPEN_SOURCE\\ E<gt>=\\ 600 || _POSIX_C_SOURCE\\ E<gt>=\\ 200112L"
1474 #: build/C/man3/mq_receive.3:76
1476 "B<mq_receive>() removes the oldest message with the highest priority from "
1477 "the message queue referred to by the descriptor I<mqdes>, and places it in "
1478 "the buffer pointed to by I<msg_ptr>. The I<msg_len> argument specifies the "
1479 "size of the buffer pointed to by I<msg_ptr>; this must be greater than the "
1480 "I<mq_msgsize> attribute of the queue (see B<mq_getattr>(3)). If I<prio> is "
1481 "not NULL, then the buffer to which it points is used to return the priority "
1482 "associated with the received message."
1486 #: build/C/man3/mq_receive.3:86
1488 "If the queue is empty, then, by default, B<mq_receive>() blocks until a "
1489 "message becomes available, or the call is interrupted by a signal handler. "
1490 "If the B<O_NONBLOCK> flag is enabled for the message queue description, then "
1491 "the call instead fails immediately with the error B<EAGAIN>."
1495 #: build/C/man3/mq_receive.3:99
1497 "B<mq_timedreceive>() behaves just like B<mq_receive>(), except that if the "
1498 "queue is empty and the B<O_NONBLOCK> flag is not enabled for the message "
1499 "queue description, then I<abs_timeout> points to a structure which specifies "
1500 "a ceiling on the time for which the call will block. This ceiling is an "
1501 "absolute timeout in seconds and nanoseconds since the Epoch, 1970-01-01 "
1502 "00:00:00 +0000 (UTC), and it is specified in the following structure:"
1506 #: build/C/man3/mq_receive.3:106 build/C/man3/mq_send.3:112
1509 "struct timespec {\n"
1510 " time_t tv_sec; /* seconds */\n"
1511 " long tv_nsec; /* nanoseconds */\n"
1516 #: build/C/man3/mq_receive.3:113
1518 "If no message is available, and the timeout has already expired by the time "
1519 "of the call, B<mq_timedreceive>() returns immediately."
1523 #: build/C/man3/mq_receive.3:122
1525 "On success, B<mq_receive>() and B<mq_timedreceive>() return the number of "
1526 "bytes in the received message; on error, -1 is returned, with I<errno> set "
1527 "to indicate the error."
1531 #: build/C/man3/mq_receive.3:123 build/C/man3/mq_send.3:128 build/C/man2/msgop.2:310 build/C/man2/msgop.2:365
1537 #: build/C/man3/mq_receive.3:129
1539 "The queue was empty, and the B<O_NONBLOCK> flag was set for the message "
1540 "queue description referred to by I<mqdes>."
1544 #: build/C/man3/mq_receive.3:134 build/C/man3/mq_send.3:139
1545 msgid "The descriptor specified in I<mqdes> was invalid."
1549 #: build/C/man3/mq_receive.3:134 build/C/man3/mq_send.3:139 build/C/man2/msgop.2:326 build/C/man2/msgop.2:380
1555 #: build/C/man3/mq_receive.3:138 build/C/man3/mq_send.3:143
1556 msgid "The call was interrupted by a signal handler; see B<signal>(7)."
1560 #: build/C/man3/mq_receive.3:147 build/C/man3/mq_send.3:152
1562 "The call would have blocked, and I<abs_timeout> was invalid, either because "
1563 "I<tv_sec> was less than zero, or because I<tv_nsec> was less than zero or "
1564 "greater than 1000 million."
1568 #: build/C/man3/mq_receive.3:147 build/C/man3/mq_send.3:152
1574 #: build/C/man3/mq_receive.3:153
1575 msgid "I<msg_len> was less than the I<mq_msgsize> attribute of the message queue."
1579 #: build/C/man3/mq_receive.3:153 build/C/man3/mq_send.3:158
1581 msgid "B<ETIMEDOUT>"
1585 #: build/C/man3/mq_receive.3:156 build/C/man3/mq_send.3:161
1586 msgid "The call timed out before a message could be transferred."
1590 #: build/C/man3/mq_receive.3:164
1592 "On Linux, B<mq_timedreceive>() is a system call, and B<mq_receive>() is a "
1593 "library function layered on top of that system call."
1597 #: build/C/man3/mq_receive.3:173
1599 "B<mq_close>(3), B<mq_getattr>(3), B<mq_notify>(3), B<mq_open>(3), "
1600 "B<mq_send>(3), B<mq_unlink>(3), B<mq_overview>(7), B<time>(7)"
1604 #: build/C/man3/mq_send.3:26
1610 #: build/C/man3/mq_send.3:29
1611 msgid "mq_send, mq_timedsend - send a message to a message queue"
1615 #: build/C/man3/mq_send.3:35
1618 "B<int mq_send(mqd_t >I<mqdes>B<, const char *>I<msg_ptr>B<,>\n"
1619 "B< size_t >I<msg_len>B<, unsigned >I<msg_prio>B<);>\n"
1623 #: build/C/man3/mq_send.3:42
1626 "B<int mq_timedsend(mqd_t >I<mqdes>B<, const char *>I<msg_ptr>B<,>\n"
1627 "B< size_t >I<msg_len>B<, unsigned >I<msg_prio>B<,>\n"
1628 "B< const struct timespec *>I<abs_timeout>B<);>\n"
1632 #: build/C/man3/mq_send.3:53
1633 msgid "B<mq_timedsend>():"
1637 #: build/C/man3/mq_send.3:71
1639 "B<mq_send>() adds the message pointed to by I<msg_ptr> to the message queue "
1640 "referred to by the descriptor I<mqdes>. The I<msg_len> argument specifies "
1641 "the length of the message pointed to by I<msg_ptr>; this length must be less "
1642 "than or equal to the queue's I<mq_msgsize> attribute. Zero-length messages "
1647 #: build/C/man3/mq_send.3:79
1649 "The I<msg_prio> argument is a nonnegative integer that specifies the "
1650 "priority of this message. Messages are placed on the queue in decreasing "
1651 "order of priority, with newer messages of the same priority being placed "
1652 "after older messages with the same priority."
1656 #: build/C/man3/mq_send.3:92
1658 "If the message queue is already full (i.e., the number of messages on the "
1659 "queue equals the queue's I<mq_maxmsg> attribute), then, by default, "
1660 "B<mq_send>() blocks until sufficient space becomes available to allow the "
1661 "message to be queued, or until the call is interrupted by a signal handler. "
1662 "If the B<O_NONBLOCK> flag is enabled for the message queue description, then "
1663 "the call instead fails immediately with the error B<EAGAIN>."
1667 #: build/C/man3/mq_send.3:105
1669 "B<mq_timedsend>() behaves just like B<mq_send>(), except that if the queue "
1670 "is full and the B<O_NONBLOCK> flag is not enabled for the message queue "
1671 "description, then I<abs_timeout> points to a structure which specifies a "
1672 "ceiling on the time for which the call will block. This ceiling is an "
1673 "absolute timeout in seconds and nanoseconds since the Epoch, 1970-01-01 "
1674 "00:00:00 +0000 (UTC), and it is specified in the following structure:"
1678 #: build/C/man3/mq_send.3:119
1680 "If the message queue is full, and the timeout has already expired by the "
1681 "time of the call, B<mq_timedsend>() returns immediately."
1685 #: build/C/man3/mq_send.3:127
1687 "On success, B<mq_send>() and B<mq_timedsend>() return zero; on error, -1 "
1688 "is returned, with I<errno> set to indicate the error."
1692 #: build/C/man3/mq_send.3:134
1694 "The queue was full, and the B<O_NONBLOCK> flag was set for the message queue "
1695 "description referred to by I<mqdes>."
1699 #: build/C/man3/mq_send.3:158
1701 "I<msg_len> was greater than the I<mq_msgsize> attribute of the message "
1706 #: build/C/man3/mq_send.3:169
1708 "On Linux, B<mq_timedsend>() is a system call, and B<mq_send>() is a "
1709 "library function layered on top of that system call."
1713 #: build/C/man3/mq_send.3:178
1715 "B<mq_close>(3), B<mq_getattr>(3), B<mq_notify>(3), B<mq_open>(3), "
1716 "B<mq_receive>(3), B<mq_unlink>(3), B<mq_overview>(7), B<time>(7)"
1720 #: build/C/man3/mq_unlink.3:26
1726 #: build/C/man3/mq_unlink.3:29
1727 msgid "mq_unlink - remove a message queue"
1731 #: build/C/man3/mq_unlink.3:34
1733 msgid "B<int mq_unlink(const char *>I<name>B<);>\n"
1737 #: build/C/man3/mq_unlink.3:44
1739 "B<mq_unlink>() removes the specified message queue I<name>. The message "
1740 "queue name is removed immediately. The queue itself is destroyed once any "
1741 "other processes that have the queue open close their descriptors referring "
1746 #: build/C/man3/mq_unlink.3:50
1748 "On success B<mq_unlink>() returns 0; on error, -1 is returned, with "
1749 "I<errno> set to indicate the error."
1753 #: build/C/man3/mq_unlink.3:54
1754 msgid "The caller does not have permission to unlink this message queue."
1758 #: build/C/man3/mq_unlink.3:62
1759 msgid "There is no message queue with the given I<name>."
1763 #: build/C/man3/mq_unlink.3:72
1765 "B<mq_close>(3), B<mq_getattr>(3), B<mq_notify>(3), B<mq_open>(3), "
1766 "B<mq_receive>(3), B<mq_send>(3), B<mq_overview>(7)"
1770 #: build/C/man2/msgctl.2:35
1776 #: build/C/man2/msgctl.2:35
1782 #: build/C/man2/msgctl.2:38
1783 msgid "msgctl - message control operations"
1787 #: build/C/man2/msgctl.2:43 build/C/man2/msgget.2:41 build/C/man2/msgop.2:46
1790 "B<#include E<lt>sys/types.hE<gt>>\n"
1791 "B<#include E<lt>sys/ipc.hE<gt>>\n"
1792 "B<#include E<lt>sys/msg.hE<gt>>\n"
1796 #: build/C/man2/msgctl.2:45
1798 msgid "B<int msgctl(int >I<msqid>B<, int >I<cmd>B<, struct msqid_ds *>I<buf>B<);>\n"
1802 #: build/C/man2/msgctl.2:52
1804 "B<msgctl>() performs the control operation specified by I<cmd> on the "
1805 "message queue with identifier I<msqid>."
1809 #: build/C/man2/msgctl.2:56
1811 "The I<msqid_ds> data structure is defined in I<E<lt>sys/msg.hE<gt>> as "
1816 #: build/C/man2/msgctl.2:73
1819 "struct msqid_ds {\n"
1820 " struct ipc_perm msg_perm; /* Ownership and permissions */\n"
1821 " time_t msg_stime; /* Time of last msgsnd(2) */\n"
1822 " time_t msg_rtime; /* Time of last msgrcv(2) */\n"
1823 " time_t msg_ctime; /* Time of last change */\n"
1824 " unsigned long __msg_cbytes; /* Current number of bytes in\n"
1825 " queue (nonstandard) */\n"
1826 " msgqnum_t msg_qnum; /* Current number of messages\n"
1828 " msglen_t msg_qbytes; /* Maximum number of bytes\n"
1829 " allowed in queue */\n"
1830 " pid_t msg_lspid; /* PID of last msgsnd(2) */\n"
1831 " pid_t msg_lrpid; /* PID of last msgrcv(2) */\n"
1836 #: build/C/man2/msgctl.2:81
1838 "The I<ipc_perm> structure is defined in I<E<lt>sys/ipc.hE<gt>> as follows "
1839 "(the highlighted fields are settable using B<IPC_SET>):"
1843 #: build/C/man2/msgctl.2:93
1846 "struct ipc_perm {\n"
1847 " key_t __key; /* Key supplied to msgget(2) */\n"
1848 " uid_t B<uid>; /* Effective UID of owner */\n"
1849 " gid_t B<gid>; /* Effective GID of owner */\n"
1850 " uid_t cuid; /* Effective UID of creator */\n"
1851 " gid_t cgid; /* Effective GID of creator */\n"
1852 " unsigned short B<mode>; /* Permissions */\n"
1853 " unsigned short __seq; /* Sequence number */\n"
1858 #: build/C/man2/msgctl.2:99
1859 msgid "Valid values for I<cmd> are:"
1863 #: build/C/man2/msgctl.2:99
1869 #: build/C/man2/msgctl.2:108
1871 "Copy information from the kernel data structure associated with I<msqid> "
1872 "into the I<msqid_ds> structure pointed to by I<buf>. The caller must have "
1873 "read permission on the message queue."
1877 #: build/C/man2/msgctl.2:108
1883 #: build/C/man2/msgctl.2:135
1885 "Write the values of some members of the I<msqid_ds> structure pointed to by "
1886 "I<buf> to the kernel data structure associated with this message queue, "
1887 "updating also its I<msg_ctime> member. The following members of the "
1888 "structure are updated: I<msg_qbytes>, I<msg_perm.uid>, I<msg_perm.gid>, and "
1889 "(the least significant 9 bits of) I<msg_perm.mode>. The effective UID of "
1890 "the calling process must match the owner (I<msg_perm.uid>) or creator "
1891 "(I<msg_perm.cuid>) of the message queue, or the caller must be privileged. "
1892 "Appropriate privilege (Linux: the B<CAP_IPC_RESOURCE> capability) is "
1893 "required to raise the I<msg_qbytes> value beyond the system parameter "
1898 #: build/C/man2/msgctl.2:135
1904 #: build/C/man2/msgctl.2:146
1906 "Immediately remove the message queue, awakening all waiting reader and "
1907 "writer processes (with an error return and I<errno> set to B<EIDRM>). The "
1908 "calling process must have appropriate privileges or its effective user ID "
1909 "must be either that of the creator or owner of the message queue."
1913 #: build/C/man2/msgctl.2:146
1915 msgid "B<IPC_INFO> (Linux-specific)"
1919 #: build/C/man2/msgctl.2:159
1921 "Returns information about system-wide message queue limits and parameters in "
1922 "the structure pointed to by I<buf>. This structure is of type I<msginfo> "
1923 "(thus, a cast is required), defined in I<E<lt>sys/msg.hE<gt>> if the "
1924 "B<_GNU_SOURCE> feature test macro is defined:"
1928 #: build/C/man2/msgctl.2:183
1931 "struct msginfo {\n"
1932 " int msgpool; /* Size in kibibytes of buffer pool\n"
1933 " used to hold message data;\n"
1934 " unused within kernel */\n"
1935 " int msgmap; /* Maximum number of entries in message\n"
1936 " map; unused within kernel */\n"
1937 " int msgmax; /* Maximum number of bytes that can be\n"
1938 " written in a single message */\n"
1939 " int msgmnb; /* Maximum number of bytes that can be\n"
1940 " written to queue; used to initialize\n"
1941 " msg_qbytes during queue creation\n"
1943 " int msgmni; /* Maximum number of message queues */\n"
1944 " int msgssz; /* Message segment size;\n"
1945 " unused within kernel */\n"
1946 " int msgtql; /* Maximum number of messages on all queues\n"
1947 " in system; unused within kernel */\n"
1948 " unsigned short int msgseg;\n"
1949 " /* Maximum number of segments;\n"
1950 " unused within kernel */\n"
1955 #: build/C/man2/msgctl.2:196
1957 "The I<msgmni>, I<msgmax>, and I<msgmnb> settings can be changed via I</proc> "
1958 "files of the same name; see B<proc>(5) for details."
1962 #: build/C/man2/msgctl.2:196
1964 msgid "B<MSG_INFO> (Linux-specific)"
1968 #: build/C/man2/msgctl.2:213
1970 "Returns a I<msginfo> structure containing the same information as for "
1971 "B<IPC_INFO>, except that the following fields are returned with information "
1972 "about system resources consumed by message queues: the I<msgpool> field "
1973 "returns the number of message queues that currently exist on the system; the "
1974 "I<msgmap> field returns the total number of messages in all queues on the "
1975 "system; and the I<msgtql> field returns the total number of bytes in all "
1976 "messages in all queues on the system."
1980 #: build/C/man2/msgctl.2:213
1982 msgid "B<MSG_STAT> (Linux-specific)"
1986 #: build/C/man2/msgctl.2:224
1988 "Returns a I<msqid_ds> structure as for B<IPC_STAT>. However, the I<msqid> "
1989 "argument is not a queue identifier, but instead an index into the kernel's "
1990 "internal array that maintains information about all message queues on the "
1995 #: build/C/man2/msgctl.2:245
1997 "On success, B<IPC_STAT>, B<IPC_SET>, and B<IPC_RMID> return 0. A successful "
1998 "B<IPC_INFO> or B<MSG_INFO> operation returns the index of the highest used "
1999 "entry in the kernel's internal array recording information about all message "
2000 "queues. (This information can be used with repeated B<MSG_STAT> operations "
2001 "to obtain information about all queues on the system.) A successful "
2002 "B<MSG_STAT> operation returns the identifier of the queue whose index was "
2003 "given in I<msqid>."
2007 #: build/C/man2/msgctl.2:249
2008 msgid "On error, -1 is returned with I<errno> indicating the error."
2012 #: build/C/man2/msgctl.2:253
2013 msgid "On failure, I<errno> is set to one of the following:"
2017 #: build/C/man2/msgctl.2:266
2019 "The argument I<cmd> is equal to B<IPC_STAT> or B<MSG_STAT>, but the calling "
2020 "process does not have read permission on the message queue I<msqid>, and "
2021 "does not have the B<CAP_IPC_OWNER> capability."
2025 #: build/C/man2/msgctl.2:266 build/C/man2/msgop.2:318 build/C/man2/msgop.2:371
2031 #: build/C/man2/msgctl.2:277
2033 "The argument I<cmd> has the value B<IPC_SET> or B<IPC_STAT>, but the address "
2034 "pointed to by I<buf> isn't accessible."
2038 #: build/C/man2/msgctl.2:277 build/C/man2/msgop.2:323 build/C/man2/msgop.2:376
2044 #: build/C/man2/msgctl.2:280 build/C/man2/msgop.2:326
2045 msgid "The message queue was removed."
2049 #: build/C/man2/msgctl.2:291
2051 "Invalid value for I<cmd> or I<msqid>. Or: for a B<MSG_STAT> operation, the "
2052 "index value specified in I<msqid> referred to an array slot that is "
2057 #: build/C/man2/msgctl.2:291
2063 #: build/C/man2/msgctl.2:309
2065 "The argument I<cmd> has the value B<IPC_SET> or B<IPC_RMID>, but the "
2066 "effective user ID of the calling process is not the creator (as found in "
2067 "I<msg_perm.cuid>) or the owner (as found in I<msg_perm.uid>) of the "
2068 "message queue, and the process is not privileged (Linux: it does not have "
2069 "the B<CAP_SYS_ADMIN> capability)."
2073 #: build/C/man2/msgctl.2:312 build/C/man2/msgget.2:183 build/C/man2/msgop.2:399
2074 msgid "SVr4, POSIX.1-2001."
2078 #: build/C/man2/msgctl.2:323
2080 "The B<IPC_INFO>, B<MSG_STAT> and B<MSG_INFO> operations are used by the "
2081 "B<ipcs>(1) program to provide information on allocated resources. In the "
2082 "future these may modified or moved to a /proc file system interface."
2086 #: build/C/man2/msgctl.2:337
2088 "Various fields in the I<struct msqid_ds> were typed as I<short> under Linux "
2089 "2.2 and have become I<long> under Linux 2.4. To take advantage of this, a "
2090 "recompilation under glibc-2.1.91 or later should suffice. (The kernel "
2091 "distinguishes old and new calls by an B<IPC_64> flag in I<cmd>.)"
2095 #: build/C/man2/msgctl.2:344
2097 "B<msgget>(2), B<msgrcv>(2), B<msgsnd>(2), B<capabilities>(7), "
2098 "B<mq_overview>(7), B<svipc>(7)"
2102 #: build/C/man2/msgget.2:33
2108 #: build/C/man2/msgget.2:33
2114 #: build/C/man2/msgget.2:36
2115 msgid "msgget - get a message queue identifier"
2119 #: build/C/man2/msgget.2:43
2121 msgid "B<int msgget(key_t >I<key>B<, int >I<msgflg>B<);>\n"
2125 #: build/C/man2/msgget.2:65
2127 "The B<msgget>() system call returns the message queue identifier associated "
2128 "with the value of the I<key> argument. A new message queue is created if "
2129 "I<key> has the value B<IPC_PRIVATE> or I<key> isn't B<IPC_PRIVATE>, no "
2130 "message queue with the given key I<key> exists, and B<IPC_CREAT> is "
2131 "specified in I<msgflg>."
2135 #: build/C/man2/msgget.2:84
2137 "If I<msgflg> specifies both B<IPC_CREAT> and B<IPC_EXCL> and a message queue "
2138 "already exists for I<key>, then B<msgget>() fails with I<errno> set to "
2139 "B<EEXIST>. (This is analogous to the effect of the combination B<O_CREAT | "
2140 "O_EXCL> for B<open>(2).)"
2144 #: build/C/man2/msgget.2:94
2146 "Upon creation, the least significant bits of the argument I<msgflg> define "
2147 "the permissions of the message queue. These permission bits have the same "
2148 "format and semantics as the permissions specified for the I<mode> argument "
2149 "of B<open>(2). (The execute permissions are not used.)"
2153 #: build/C/man2/msgget.2:101
2155 "If a new message queue is created, then its associated data structure "
2156 "I<msqid_ds> (see B<msgctl>(2)) is initialized as follows:"
2160 #: build/C/man2/msgget.2:106
2162 "I<msg_perm.cuid> and I<msg_perm.uid> are set to the effective user ID of the "
2167 #: build/C/man2/msgget.2:111
2169 "I<msg_perm.cgid> and I<msg_perm.gid> are set to the effective group ID of "
2170 "the calling process."
2174 #: build/C/man2/msgget.2:116
2176 "The least significant 9 bits of I<msg_perm.mode> are set to the least "
2177 "significant 9 bits of I<msgflg>."
2181 #: build/C/man2/msgget.2:124
2183 "I<msg_qnum>, I<msg_lspid>, I<msg_lrpid>, I<msg_stime> and I<msg_rtime> are "
2188 #: build/C/man2/msgget.2:127
2189 msgid "I<msg_ctime> is set to the current time."
2193 #: build/C/man2/msgget.2:131
2194 msgid "I<msg_qbytes> is set to the system limit B<MSGMNB>."
2198 #: build/C/man2/msgget.2:135
2200 "If the message queue already exists the permissions are verified, and a "
2201 "check is made to see if it is marked for destruction."
2205 #: build/C/man2/msgget.2:141
2207 "If successful, the return value will be the message queue identifier (a "
2208 "nonnegative integer), otherwise -1 with I<errno> indicating the error."
2212 #: build/C/man2/msgget.2:145
2213 msgid "On failure, I<errno> is set to one of the following values:"
2217 #: build/C/man2/msgget.2:153
2219 "A message queue exists for I<key>, but the calling process does not have "
2220 "permission to access the queue, and does not have the B<CAP_IPC_OWNER> "
2225 #: build/C/man2/msgget.2:163
2227 "A message queue exists for I<key> and I<msgflg> specified both B<IPC_CREAT> "
2232 #: build/C/man2/msgget.2:171
2234 "No message queue exists for I<key> and I<msgflg> did not specify "
2239 #: build/C/man2/msgget.2:175
2241 "A message queue has to be created but the system does not have enough memory "
2242 "for the new data structure."
2246 #: build/C/man2/msgget.2:181
2248 "A message queue has to be created but the system limit for the maximum "
2249 "number of message queues (B<MSGMNI>) would be exceeded."
2253 #: build/C/man2/msgget.2:193
2255 "B<IPC_PRIVATE> isn't a flag field but a I<key_t> type. If this special "
2256 "value is used for I<key>, the system call ignores everything but the least "
2257 "significant 9 bits of I<msgflg> and creates a new message queue (on "
2262 #: build/C/man2/msgget.2:197
2264 "The following is a system limit on message queue resources affecting a "
2269 #: build/C/man2/msgget.2:197
2275 #: build/C/man2/msgget.2:203
2277 "System wide maximum number of message queues: policy dependent (on Linux, "
2278 "this limit can be read and modified via I</proc/sys/kernel/msgmni>)."
2282 #: build/C/man2/msgget.2:203
2288 #: build/C/man2/msgget.2:209
2290 "Until version 2.3.20 Linux would return B<EIDRM> for a B<msgget>() on a "
2291 "message queue scheduled for deletion."
2295 #: build/C/man2/msgget.2:215
2297 "The name choice B<IPC_PRIVATE> was perhaps unfortunate, B<IPC_NEW> would "
2298 "more clearly show its function."
2302 #: build/C/man2/msgget.2:223
2304 "B<msgctl>(2), B<msgrcv>(2), B<msgsnd>(2), B<ftok>(3), B<capabilities>(7), "
2305 "B<mq_overview>(7), B<svipc>(7)"
2309 #: build/C/man2/msgop.2:38
2315 #: build/C/man2/msgop.2:38
2321 #: build/C/man2/msgop.2:41
2322 msgid "msgrcv, msgsnd - message operations"
2326 #: build/C/man2/msgop.2:49
2329 "B<int msgsnd(int >I<msqid>B<, const void *>I<msgp>B<, size_t >I<msgsz>B<, "
2330 "int >I<msgflg>B<);>\n"
2334 #: build/C/man2/msgop.2:53
2337 "B<ssize_t msgrcv(int >I<msqid>B<, void *>I<msgp>B<, size_t >I<msgsz>B<, long "
2339 "B< int >I<msgflg>B<);>\n"
2343 #: build/C/man2/msgop.2:63
2345 "The B<msgsnd>() and B<msgrcv>() system calls are used, respectively, to "
2346 "send messages to, and receive messages from, a message queue. The calling "
2347 "process must have write permission on the message queue in order to send a "
2348 "message, and read permission to receive a message."
2352 #: build/C/man2/msgop.2:68
2354 "The I<msgp> argument is a pointer to caller-defined structure of the "
2355 "following general form:"
2359 #: build/C/man2/msgop.2:75
2363 " long mtype; /* message type, must be E<gt> 0 */\n"
2364 " char mtext[1]; /* message data */\n"
2369 #: build/C/man2/msgop.2:94
2371 "The I<mtext> field is an array (or other structure) whose size is specified "
2372 "by I<msgsz>, a nonnegative integer value. Messages of zero length (i.e., no "
2373 "I<mtext> field) are permitted. The I<mtype> field must have a strictly "
2374 "positive integer value. This value can be used by the receiving process for "
2375 "message selection (see the description of B<msgrcv>() below)."
2379 #: build/C/man2/msgop.2:94
2385 #: build/C/man2/msgop.2:102
2387 "The B<msgsnd>() system call appends a copy of the message pointed to by "
2388 "I<msgp> to the message queue whose identifier is specified by I<msqid>."
2392 #: build/C/man2/msgop.2:123
2394 "If sufficient space is available in the queue, B<msgsnd>() succeeds "
2395 "immediately. (The queue capacity is defined by the I<msg_qbytes> field in "
2396 "the associated data structure for the message queue. During queue creation "
2397 "this field is initialized to B<MSGMNB> bytes, but this limit can be modified "
2398 "using B<msgctl>(2).) If insufficient space is available in the queue, then "
2399 "the default behavior of B<msgsnd>() is to block until space becomes "
2400 "available. If B<IPC_NOWAIT> is specified in I<msgflg>, then the call "
2401 "instead fails with the error B<EAGAIN>."
2405 #: build/C/man2/msgop.2:127
2406 msgid "A blocked B<msgsnd>() call may also fail if:"
2410 #: build/C/man2/msgop.2:127 build/C/man2/msgop.2:134 build/C/man2/msgop.2:196 build/C/man2/msgop.2:201 build/C/man2/msgop.2:215 build/C/man2/msgop.2:254 build/C/man2/msgop.2:256 build/C/man2/msgop.2:262
2416 #: build/C/man2/msgop.2:134
2418 "the queue is removed, in which case the system call fails with I<errno> set "
2423 #: build/C/man2/msgop.2:146
2425 "a signal is caught, in which case the system call fails with I<errno> set to "
2426 "B<EINTR>;B<see> B<signal>(7). (B<msgsnd>() is never automatically "
2427 "restarted after being interrupted by a signal handler, regardless of the "
2428 "setting of the B<SA_RESTART> flag when establishing a signal handler.)"
2432 #: build/C/man2/msgop.2:149 build/C/man2/msgop.2:276
2434 "Upon successful completion the message queue data structure is updated as "
2439 #: build/C/man2/msgop.2:152
2440 msgid "I<msg_lspid> is set to the process ID of the calling process."
2444 #: build/C/man2/msgop.2:155
2445 msgid "I<msg_qnum> is incremented by 1."
2449 #: build/C/man2/msgop.2:158
2450 msgid "I<msg_stime> is set to the current time."
2454 #: build/C/man2/msgop.2:158
2460 #: build/C/man2/msgop.2:166
2462 "The B<msgrcv>() system call removes a message from the queue specified by "
2463 "I<msqid> and places it in the buffer pointed to by I<msgp>."
2467 #: build/C/man2/msgop.2:192
2469 "The argument I<msgsz> specifies the maximum size in bytes for the member "
2470 "I<mtext> of the structure pointed to by the I<msgp> argument. If the "
2471 "message text has length greater than I<msgsz>, then the behavior depends on "
2472 "whether B<MSG_NOERROR> is specified in I<msgflg>. If B<MSG_NOERROR> is "
2473 "specified, then the message text will be truncated (and the truncated part "
2474 "will be lost); if B<MSG_NOERROR> is not specified, then the message isn't "
2475 "removed from the queue and the system call fails returning -1 with I<errno> "
2480 #: build/C/man2/msgop.2:196
2481 msgid "The argument I<msgtyp> specifies the type of message requested as follows:"
2485 #: build/C/man2/msgop.2:201
2486 msgid "If I<msgtyp> is 0, then the first message in the queue is read."
2490 #: build/C/man2/msgop.2:215
2492 "If I<msgtyp> is greater than 0, then the first message in the queue of type "
2493 "I<msgtyp> is read, unless B<MSG_EXCEPT> was specified in I<msgflg>, in which "
2494 "case the first message in the queue of type not equal to I<msgtyp> will be "
2499 #: build/C/man2/msgop.2:223
2501 "If I<msgtyp> is less than 0, then the first message in the queue with the "
2502 "lowest type less than or equal to the absolute value of I<msgtyp> will be "
2507 #: build/C/man2/msgop.2:228
2509 "The I<msgflg> argument is a bit mask constructed by ORing together zero or "
2510 "more of the following flags:"
2514 #: build/C/man2/msgop.2:228
2516 msgid "B<IPC_NOWAIT>"
2520 #: build/C/man2/msgop.2:235
2522 "Return immediately if no message of the requested type is in the queue. The "
2523 "system call fails with I<errno> set to B<ENOMSG>."
2527 #: build/C/man2/msgop.2:235
2529 msgid "B<MSG_EXCEPT>"
2533 #: build/C/man2/msgop.2:243
2535 "Used with I<msgtyp> greater than 0 to read the first message in the queue "
2536 "with message type that differs from I<msgtyp>."
2540 #: build/C/man2/msgop.2:243
2542 msgid "B<MSG_NOERROR>"
2546 #: build/C/man2/msgop.2:248
2547 msgid "To truncate the message text if longer than I<msgsz> bytes."
2551 #: build/C/man2/msgop.2:254
2553 "If no message of the requested type is available and B<IPC_NOWAIT> isn't "
2554 "specified in I<msgflg>, the calling process is blocked until one of the "
2555 "following conditions occurs:"
2559 #: build/C/man2/msgop.2:256
2560 msgid "A message of the desired type is placed in the queue."
2564 #: build/C/man2/msgop.2:262
2566 "The message queue is removed from the system. In this case the system call "
2567 "fails with I<errno> set to B<EIDRM>."
2571 #: build/C/man2/msgop.2:273
2573 "The calling process catches a signal. In this case the system call fails "
2574 "with I<errno> set to B<EINTR>. (B<msgrcv>() is never automatically "
2575 "restarted after being interrupted by a signal handler, regardless of the "
2576 "setting of the B<SA_RESTART> flag when establishing a signal handler.)"
2580 #: build/C/man2/msgop.2:279
2581 msgid "I<msg_lrpid> is set to the process ID of the calling process."
2585 #: build/C/man2/msgop.2:282
2586 msgid "I<msg_qnum> is decremented by 1."
2590 #: build/C/man2/msgop.2:285
2591 msgid "I<msg_rtime> is set to the current time."
2595 #: build/C/man2/msgop.2:298
2597 "On failure both functions return -1 with I<errno> indicating the error, "
2598 "otherwise B<msgsnd>() returns 0 and B<msgrcv>() returns the number of "
2599 "bytes actually copied into the I<mtext> array."
2603 #: build/C/man2/msgop.2:304
2605 "When B<msgsnd>() fails, I<errno> will be set to one among the following "
2610 #: build/C/man2/msgop.2:310
2612 "The calling process does not have write permission on the message queue, and "
2613 "does not have the B<CAP_IPC_OWNER> capability."
2617 #: build/C/man2/msgop.2:318
2619 "The message can't be sent due to the I<msg_qbytes> limit for the queue and "
2620 "B<IPC_NOWAIT> was specified in I<msgflg>."
2624 #: build/C/man2/msgop.2:323 build/C/man2/msgop.2:376
2625 msgid "The address pointed to by I<msgp> isn't accessible."
2629 #: build/C/man2/msgop.2:329
2630 msgid "Sleeping on a full message queue condition, the process caught a signal."
2634 #: build/C/man2/msgop.2:340
2636 "Invalid I<msqid> value, or nonpositive I<mtype> value, or invalid I<msgsz> "
2637 "value (less than 0 or greater than the system value B<MSGMAX>)."
2641 #: build/C/man2/msgop.2:345
2643 "The system does not have enough memory to make a copy of the message pointed "
2648 #: build/C/man2/msgop.2:351
2650 "When B<msgrcv>() fails, I<errno> will be set to one among the following "
2655 #: build/C/man2/msgop.2:351
2661 #: build/C/man2/msgop.2:359
2663 "The message text length is greater than I<msgsz> and B<MSG_NOERROR> isn't "
2664 "specified in I<msgflg>."
2668 #: build/C/man2/msgop.2:365
2670 "The calling process does not have read permission on the message queue, and "
2671 "does not have the B<CAP_IPC_OWNER> capability."
2675 #: build/C/man2/msgop.2:371
2677 "No message was available in the queue and B<IPC_NOWAIT> was specified in "
2682 #: build/C/man2/msgop.2:380
2684 "While the process was sleeping to receive a message, the message queue was "
2689 #: build/C/man2/msgop.2:385
2691 "While the process was sleeping to receive a message, the process caught a "
2692 "signal; see B<signal>(7)."
2696 #: build/C/man2/msgop.2:391
2697 msgid "I<msgqid> was invalid, or I<msgsz> was less than 0."
2701 #: build/C/man2/msgop.2:391
2707 #: build/C/man2/msgop.2:397
2709 "B<IPC_NOWAIT> was specified in I<msgflg> and no message of the requested "
2710 "type existed on the message queue."
2714 #: build/C/man2/msgop.2:406
2716 "The I<msgp> argument is declared as I<struct msgbuf *> with libc4, libc5, "
2717 "glibc 2.0, glibc 2.1. It is declared as I<void *> with glibc 2.2 and later, "
2718 "as required by SUSv2 and SUSv3."
2722 #: build/C/man2/msgop.2:410
2724 "The following limits on message queue resources affect the B<msgsnd>() "
2729 #: build/C/man2/msgop.2:410
2735 #: build/C/man2/msgop.2:415
2737 "Maximum size for a message text: 8192 bytes (on Linux, this limit can be "
2738 "read and modified via I</proc/sys/kernel/msgmax>)."
2742 #: build/C/man2/msgop.2:415
2748 #: build/C/man2/msgop.2:425
2750 "Default maximum size in bytes of a message queue: 16384 bytes (on Linux, "
2751 "this limit can be read and modified via I</proc/sys/kernel/msgmnb>). The "
2752 "superuser can increase the size of a message queue beyond B<MSGMNB> by a "
2753 "B<msgctl>(2) system call."
2757 #: build/C/man2/msgop.2:431
2759 "The implementation has no intrinsic limits for the system wide maximum "
2760 "number of message headers (B<MSGTQL>) and for the system wide maximum size "
2761 "in bytes of the message pool (B<MSGPOOL>)."
2765 #: build/C/man2/msgop.2:437
2767 "B<msgctl>(2), B<msgget>(2), B<capabilities>(7), B<mq_overview>(7), "