IPC-msg 消息队列

int msgget(key_t key, int msgflg);
int msgsnd(int msqid, const void *msgp, size_t msgsz, int msgflg);
ssize_t msgrcv(int msqid, void *msgp, size_t msgsz, long msgtyp,int msgflg);
       int msgctl(int msqid, int cmd, struct msqid_ds *buf);

[root@localhost ch14]# cat msg1.c
/* Here's the receiver program. */

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

#include <sys/msg.h>

struct my_msg_st {
long int my_msg_type;
char some_text[BUFSIZ];
};

int main()
{
printf("BUFSIZ:%d\n",BUFSIZ);
int running = 1;
int msgid;
struct my_msg_st some_data;
long int msg_to_receive = 0;

/* First, we set up the message queue. */

msgid = msgget((key_t)1234, 0666 | IPC_CREAT);

if (msgid == -1) {
fprintf(stderr, "msgget failed with error: %d\n", errno);
exit(EXIT_FAILURE);
}

/* Then the messages are retrieved from the queue, until an end message is encountered.
Lastly, the message queue is deleted. */

while(running) {
if (msgrcv(msgid, (void *)&some_data, BUFSIZ,
msg_to_receive, 0) == -1) {
fprintf(stderr, "msgrcv failed with error: %d\n", errno);
exit(EXIT_FAILURE);
}
printf("You wrote: %s", some_data.some_text);
if (strncmp(some_data.some_text, "end", 3) == 0) {
running = 0;
}
}

if (msgctl(msgid, IPC_RMID, 0) == -1) {
fprintf(stderr, "msgctl(IPC_RMID) failed\n");
exit(EXIT_FAILURE);
}

exit(EXIT_SUCCESS);
}
[root@localhost ch14]#
[root@localhost ch14]# cat msg2.c
/* The sender program is very similar to msg1.c. In the main set up, delete the
msg_to_receive declaration and replace it with buffer[BUFSIZ], remove the message
queue delete and make the following changes to the running loop.
We now have a call to msgsnd to send the entered text to the queue. */

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

#include <sys/msg.h>

#define MAX_TEXT 512

struct my_msg_st {
long int my_msg_type;
char some_text[MAX_TEXT];
};

int main()
{
int running = 1;
struct my_msg_st some_data;
int msgid;
char buffer[BUFSIZ];

msgid = msgget((key_t)1234, 0666 | IPC_CREAT);

if (msgid == -1) {
fprintf(stderr, "msgget failed with error: %d\n", errno);
exit(EXIT_FAILURE);
}

while(running) {
usleep(1000);//1ms
printf("Enter some text: ");
fgets(buffer, BUFSIZ, stdin);
some_data.my_msg_type = 1;
strcpy(some_data.some_text, buffer);

if (msgsnd(msgid, (void *)&some_data, MAX_TEXT, 0) == -1) {
fprintf(stderr, "msgsnd failed\n");
exit(EXIT_FAILURE);
}
if (strncmp(buffer, "end", 3) == 0) {
running = 0;
}
}

exit(EXIT_SUCCESS);
}
[root@localhost ch14]#

[root@localhost ch14]# ./msg1&
[2] 6998
[root@localhost ch14]# BUFSIZ:8192
./msg2
Enter some text: hello
You wrote: hello
Enter some text: en
You wrote: en
Enter some text: