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Diffstat (limited to 'man3/mq_getattr.3')
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diff --git a/man3/mq_getattr.3 b/man3/mq_getattr.3 deleted file mode 100644 index 7c124ea..0000000 --- a/man3/mq_getattr.3 +++ /dev/null @@ -1,229 +0,0 @@ -'\" t -.\" Copyright (C) 2006 Michael Kerrisk <mtk.manpages@gmail.com> -.\" -.\" SPDX-License-Identifier: Linux-man-pages-copyleft -.\" -.TH mq_getattr 3 2023-10-31 "Linux man-pages 6.7" -.SH NAME -mq_getattr, mq_setattr \- get/set message queue attributes -.SH LIBRARY -Real-time library -.RI ( librt ", " \-lrt ) -.SH SYNOPSIS -.nf -.B #include <mqueue.h> -.P -.BI "int mq_getattr(mqd_t " mqdes ", struct mq_attr *" attr ); -.BI "int mq_setattr(mqd_t " mqdes ", const struct mq_attr *restrict " newattr , -.BI " struct mq_attr *restrict " oldattr ); -.fi -.SH DESCRIPTION -.BR mq_getattr () -and -.BR mq_setattr () -respectively retrieve and modify attributes of the message queue -referred to by the message queue descriptor -.IR mqdes . -.P -.BR mq_getattr () -returns an -.I mq_attr -structure in the buffer pointed by -.IR attr . -This structure is defined as: -.P -.in +4n -.EX -struct mq_attr { - long mq_flags; /* Flags: 0 or O_NONBLOCK */ - long mq_maxmsg; /* Max. # of messages on queue */ - long mq_msgsize; /* Max. message size (bytes) */ - long mq_curmsgs; /* # of messages currently in queue */ -}; -.EE -.in -.P -The -.I mq_flags -field contains flags associated with the open message queue description. -This field is initialized when the queue is created by -.BR mq_open (3). -The only flag that can appear in this field is -.BR O_NONBLOCK . -.P -The -.I mq_maxmsg -and -.I mq_msgsize -fields are set when the message queue is created by -.BR mq_open (3). -The -.I mq_maxmsg -field is an upper limit on the number of messages -that may be placed on the queue using -.BR mq_send (3). -The -.I mq_msgsize -field is an upper limit on the size of messages -that may be placed on the queue. -Both of these fields must have a value greater than zero. -Two -.I /proc -files that place ceilings on the values for these fields are described in -.BR mq_overview (7). -.P -The -.I mq_curmsgs -field returns the number of messages currently held in the queue. -.P -.BR mq_setattr () -sets message queue attributes using information supplied in the -.I mq_attr -structure pointed to by -.IR newattr . -The only attribute that can be modified is the setting of the -.B O_NONBLOCK -flag in -.IR mq_flags . -The other fields in -.I newattr -are ignored. -If the -.I oldattr -field is not NULL, -then the buffer that it points to is used to return an -.I mq_attr -structure that contains the same information that is returned by -.BR mq_getattr (). -.SH RETURN VALUE -On success -.BR mq_getattr () -and -.BR mq_setattr () -return 0; on error, \-1 is returned, with -.I errno -set to indicate the error. -.SH ERRORS -.TP -.B EBADF -The message queue descriptor specified in -.I mqdes -is invalid. -.TP -.B EINVAL -.I newattr\->mq_flags -contained set bits other than -.BR O_NONBLOCK . -.SH ATTRIBUTES -For an explanation of the terms used in this section, see -.BR attributes (7). -.TS -allbox; -lbx lb lb -l l l. -Interface Attribute Value -T{ -.na -.nh -.BR mq_getattr (), -.BR mq_setattr () -T} Thread safety MT-Safe -.TE -.SH VERSIONS -On Linux, -.BR mq_getattr () -and -.BR mq_setattr () -are library functions layered on top of the -.BR mq_getsetattr (2) -system call. -.SH STANDARDS -POSIX.1-2008. -.SH HISTORY -POSIX.1-2001. -.SH EXAMPLES -The program below can be used to show the default -.I mq_maxmsg -and -.I mq_msgsize -values that are assigned to a message queue that is created with a call to -.BR mq_open (3) -in which the -.I attr -argument is NULL. -Here is an example run of the program: -.P -.in +4n -.EX -$ \fB./a.out /testq\fP -Maximum # of messages on queue: 10 -Maximum message size: 8192 -.EE -.in -.P -Since Linux 3.5, the following -.I /proc -files (described in -.BR mq_overview (7)) -can be used to control the defaults: -.P -.in +4n -.EX -$ \fBuname \-sr\fP -Linux 3.8.0 -$ \fBcat /proc/sys/fs/mqueue/msg_default\fP -10 -$ \fBcat /proc/sys/fs/mqueue/msgsize_default\fP -8192 -.EE -.in -.SS Program source -\& -.\" SRC BEGIN (mq_getattr.c) -.EX -#include <fcntl.h> -#include <mqueue.h> -#include <stdio.h> -#include <stdlib.h> -#include <sys/stat.h> -#include <unistd.h> -\& -#define errExit(msg) do { perror(msg); exit(EXIT_FAILURE); \e - } while (0) -\& -int -main(int argc, char *argv[]) -{ - mqd_t mqd; - struct mq_attr attr; -\& - if (argc != 2) { - fprintf(stderr, "Usage: %s mq\-name\en", argv[0]); - exit(EXIT_FAILURE); - } -\& - mqd = mq_open(argv[1], O_CREAT | O_EXCL, 0600, NULL); - if (mqd == (mqd_t) \-1) - errExit("mq_open"); -\& - if (mq_getattr(mqd, &attr) == \-1) - errExit("mq_getattr"); -\& - printf("Maximum # of messages on queue: %ld\en", attr.mq_maxmsg); - printf("Maximum message size: %ld\en", attr.mq_msgsize); -\& - if (mq_unlink(argv[1]) == \-1) - errExit("mq_unlink"); -\& - exit(EXIT_SUCCESS); -} -.EE -.\" SRC END -.SH SEE ALSO -.BR mq_close (3), -.BR mq_notify (3), -.BR mq_open (3), -.BR mq_receive (3), -.BR mq_send (3), -.BR mq_unlink (3), -.BR mq_overview (7) |