Unix/Linux进程间通信——（System V）消息队列

System V消息队列实例：

/* http://beej.us/guide/bgipc/examples/kirk.c */
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/msg.h>

struct my_msgbuf {
	long mtype;
	char mtext[200];
};

int main(void)
{
	struct my_msgbuf buf;
	int msqid;
	key_t key;

	if ((key = ftok("kirk.c", 'B')) == -1) {
		perror("ftok");
		exit(1);
	}

	if ((msqid = msgget(key, 0644 | IPC_CREAT)) == -1) {
		perror("msgget");
		exit(1);
	}

	printf("Enter lines of text, ^D to quit:\n");

	buf.mtype = 1; /* we don't really care in this case */

	while(fgets(buf.mtext, sizeof(buf.mtext), stdin) != NULL) {
		int len = strlen(buf.mtext);

		/* ditch newline at end, if it exists */
		if (buf.mtext[len-1] == '\n') buf.mtext[len-1] = '\0';

		if (msgsnd(msqid, &buf, len+1, 0) == -1) /* +1 for '\0' */
			perror("msgsnd");
	}

	if (msgctl(msqid, IPC_RMID, NULL) == -1) {
		perror("msgctl");
		exit(1);
	}

	return 0;
}

/* http://beej.us/guide/bgipc/examples/spock.c */
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/msg.h>

struct my_msgbuf {
	long mtype;
	char mtext[200];
};

int main(void)
{
	struct my_msgbuf buf;
	int msqid;
	key_t key;

	if ((key = ftok("kirk.c", 'B')) == -1) { /* same key as kirk.c */
		perror("ftok");
		exit(1);
	}

	if ((msqid = msgget(key, 0644)) == -1) { /* connect to the queue */
		perror("msgget");
		exit(1);
	}

	printf("spock: ready to receive messages, captain.\n");

	for (;;) { /* Spock never quits! */
		if (msgrcv(msqid, &buf, sizeof(buf.mtext), 0, 0) == -1) {
			perror("msgrcv");
			exit(1);
		}
		printf("spock: \"%s\"\n", buf.mtext);
	}

	return 0;
}