プロセス間通信(IPC):メッセージキュー(Message Queue)
3418 ワード
メッセージ・キューは、名前付きパイプと似ていますが、パイプの開閉の複雑さは少なくなります.名前付きパイプと比較して、メッセージキューの利点は、送信および受信プロセスとは独立して存在することです.
メッセージキュー関数の定義は次のとおりです.
msg1.cメッセージの受信に用いるmsg 2.cメッセージ送信用
msg1.c
msg2.c
メッセージキュー関数の定義は次のとおりです.
#include
int msgctl(int msqid, int cmd, struct msqid_ds *buf);//
int msgget(key_t key, int msgflg);//
int msgrcv(int msqid, void *msg_ptr, size_t msg_sz, long int msgtype, int msgflg);//
int msgsnd(int msqid, const void *msg_ptr,size_tmsg_sz,int msgflg);//
msg1.cメッセージの受信に用いるmsg 2.cメッセージ送信用
msg1.c
/* Here's the receiver program. */
#include
#include
#include
#include
#include
#include
struct my_msg_st {
long int my_msg_type;
char some_text[BUFSIZ];
};
int main()
{
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
", 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
", 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
");
exit(EXIT_FAILURE);
}
exit(EXIT_SUCCESS);
}
~
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
#include
#include
#include
#include
#include
#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
", errno);
exit(EXIT_FAILURE);
}
while(running) {
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
");
exit(EXIT_FAILURE);
}
if (strncmp(buffer, "end", 3) == 0) {
running = 0;
}
}
exit(EXIT_SUCCESS);
}
./msg2
Enter some text: hi
Enter some text: jiajia
Enter some text: end
./msg1
You wrote: hi
You wrote: jiajia
You wrote: end