创建自定义属性的POSIX消息队列

#include <stdio.h>
#include <fcntl.h>
#include <errno.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <mqueue.h>

struct mq_attr attr;
const int maxline=4096;

int main(int argc, char **argv) {
	int c, flags;
	mqd_t mqd;
	char errbuff[maxline];

	flags=O_RDWR | O_CREAT;
	while((c=getopt(argc, argv, "em:z:"))!=-1) {
		switch(c) {
			case 'e':
				flags|=O_EXCL;
				break;
			case 'm':
				attr.mq_maxmsg=atol(optarg);
				break;
			case 'z':
				attr.mq_msgsize=atol(optarg);
				break;
		}
	}

	if(optind != argc-1) {
		fprintf(stderr, "mqcreate [-e] [ -m maxmsg -z msgsize ] <name>\n");
		exit(-1);
	}

	if((attr.mq_maxmsg!=0&&attr.mq_msgsize==0) || (attr.mq_maxmsg==0&&attr.mq_msgsize!=0)) {
		fprintf(stderr, "must specify both -m maxmsg -z msgsize\n");
		exit(-1);
	}

	if((mqd=mq_open(argv[optind], flags, S_IRUSR|S_IWUSR|S_IRGRP|S_IROTH, (attr.mq_maxmsg!=0) ? &attr:NULL))<0) {
		strerror_r(errno, errbuff, maxline);
		fprintf(stderr, "mq_open error: %s\n", errbuff);
		exit(-1);
	}

	mq_close(mqd);
	
	exit(0);
}

指定创建队列的最大消息数和每个消息的最大大小