Linux 进程间通信(IPC)之三 --- 共享内存

场景：
    两个进程，A进程创建共享内存并读取数据；B进程连接共享内存写入数据。输入 end 结束进程。

应用实例：

头文件：shm_com.h

 

01.#include <unistd.h>
02.#include <stdlib.h>
03.#include <stdio.h>
04.#include <sys/types.h>
05.#include <sys/ipc.h>
06.#include <sys/shm.h>
07.
08.#define TEXT_SZ 2048
09.
10.struct  shared_use_st{
11.    int written_by_you;
12.    char    some_text[TEXT_SZ];
13.};

消费者程序：shm_customer.h消费者程序：shm_customer.h消费者程序：shm_customer.h

 

01.#include "shm_com.h"
02.
03.int main(int argc,char **argv)
04.{
05.    int running = 1;
06.    void *shared_memory = (void *)0;
07.    struct  shared_use_st *shared_stuff;
08.    int shmid;
09.
10.    srand((unsigned int)getpid());
11.
12.    shmid = shmget((key_t)1234,sizeof(struct shared_use_st),0666|IPC_CREAT);
13.    if(shmid == -1){
14.        fprintf(stderr,"shmget failed\n");
15.        exit(-1);
16.    }
17.
18.    shared_memory = shmat(shmid,(void *)0,0);
19.    if(shared_memory == (void *)-1){
20.        fprintf(stderr,"shmat failed\n");
21.        exit(-1);
22.    }
23.
24.    shared_stuff = (struct shared_use_st *)shared_memory;
25.    shared_stuff->written_by_you = 0;
26.    while(running){
27.        if(shared_stuff->written_by_you){
28.            printf("You wrote: %s",shared_stuff->some_text);
29.            sleep(rand()%4);
30.            shared_stuff->written_by_you = 0;
31.            if(strncmp(shared_stuff->some_text,"end",3) == 0){
32.                running = 0;
33.            }
34.        }
35.    }
36.
37.    if(shmdt(shared_memory) == -1){
38.        fprintf(stderr,"shmdt failed!\n");
39.        exit(-1);
40.    }
41.
42.    if(shmctl(shmid,IPC_RMID,0) == -1){
43.        fprintf(stderr,"shmctl(IPC_RMID) failed!\n");
44.        exit(-1);
45.    }
46.
47.    exit(0);
48.}

 

生产者程序：shm_producer.c

01.#include "shm_com.h"
02.
03.int main(int argc,char **argv)
04.{
05.    int running = 1;
06.    void *shared_memory = (void *)0;
07.    struct  shared_use_st *shared_stuff;
08.    char    buffer[TEXT_SZ];
09.    int shmid;
10.
11.    shmid = shmget((key_t)1234,sizeof(struct shared_use_st),0666|IPC_CREAT);
12.    if(shmid == -1){
13.        fprintf(stderr,"Shmget failed!\n");
14.        exit(-1);
15.    }
16.
17.    shared_memory = shmat(shmid,(void *)0,0);
18.    if(shared_memory == (void *)-1){
19.        fprintf(stderr,"Shmat failed!\n");
20.        exit(-1);
21.    }
22.
23.    printf("Memory attached at %X\n",(int)shared_memory);
24.
25.    shared_stuff = (struct shared_use_st *)shared_memory;
26.    while(running){
27.        while(shared_stuff->written_by_you == 1){
28.            sleep(1);
29.            printf("Waiting for client...\n");
30.        }
31.        printf("Enter some text: ");
32.        fgets(buffer,TEXT_SZ,stdin);
33.
34.        strncpy(shared_stuff->some_text,buffer,TEXT_SZ);
35.        shared_stuff->written_by_you = 1;
36.
37.        if(strncmp(buffer,"end",3) == 0){
38.            running = 0;
39.        }
40.    }
41.
42.    if(shmdt(shared_memory) == -1){
43.        fprintf(stderr,"Shmdt failed\n");
44.        exit(-1);
45.    }
46.
47.    exit(0);
48.}

 

生产者程序：shm_producer.c生产者程序：shm_producer.c生产者程序：shm_producer.c生产者程序：shm_producer.c生产者程序：shm_producer.c