Linux进程间通信——共享内存
- int shmget(key_t key, size_t size, int shmflg);
- void *shmat(int shm_id, const void *shm_addr, int shmflg);
- int shmdt(const void *shmaddr);
- int shmctl(int shm_id, int command, struct shmid_ds *buf);
- struct shmid_ds
- {
- uid_t shm_perm.uid;
- uid_t shm_perm.gid;
- mode_t shm_perm.mode;
- };
- #ifndef _SHMDATA_H_HEADER
- #define _SHMDATA_H_HEADER
- #define TEXT_SZ 2048
- struct shared_use_st
- {
- int written;//作为一个标志,非0:表示可读,0表示可写
- char text[TEXT_SZ];//记录写入和读取的文本
- };
- #endif
- #include <unistd.h>
- #include <stdlib.h>
- #include <stdio.h>
- #include <sys/shm.h>
- #include "shmdata.h"
- int main()
- {
- int running = 1;//程序是否继续运行的标志
- void *shm = NULL;//分配的共享内存的原始首地址
- struct shared_use_st *shared;//指向shm
- int shmid;//共享内存标识符
- //创建共享内存
- shmid = shmget((key_t)1234, sizeof(struct shared_use_st), 0666|IPC_CREAT);
- if(shmid == -1)
- {
- fprintf(stderr, "shmget failed\n");
- exit(EXIT_FAILURE);
- }
- //将共享内存连接到当前进程的地址空间
- shm = shmat(shmid, 0, 0);
- if(shm == (void*)-1)
- {
- fprintf(stderr, "shmat failed\n");
- exit(EXIT_FAILURE);
- }
- printf("\nMemory attached at %X\n", (int)shm);
- //设置共享内存
- shared = (struct shared_use_st*)shm;
- shared->written = 0;
- while(running)//读取共享内存中的数据
- {
- //没有进程向共享内存定数据有数据可读取
- if(shared->written != 0)
- {
- printf("You wrote: %s", shared->text);
- sleep(rand() % 3);
- //读取完数据,设置written使共享内存段可写
- shared->written = 0;
- //输入了end,退出循环(程序)
- if(strncmp(shared->text, "end", 3) == 0)
- running = 0;
- }
- else//有其他进程在写数据,不能读取数据
- sleep(1);
- }
- //把共享内存从当前进程中分离
- if(shmdt(shm) == -1)
- {
- fprintf(stderr, "shmdt failed\n");
- exit(EXIT_FAILURE);
- }
- //删除共享内存
- if(shmctl(shmid, IPC_RMID, 0) == -1)
- {
- fprintf(stderr, "shmctl(IPC_RMID) failed\n");
- exit(EXIT_FAILURE);
- }
- exit(EXIT_SUCCESS);
- }
- #include <unistd.h>
- #include <stdlib.h>
- #include <stdio.h>
- #include <string.h>
- #include <sys/shm.h>
- #include "shmdata.h"
- int main()
- {
- int running = 1;
- void *shm = NULL;
- struct shared_use_st *shared = NULL;
- char buffer[BUFSIZ + 1];//用于保存输入的文本
- int shmid;
- //创建共享内存
- shmid = shmget((key_t)1234, sizeof(struct shared_use_st), 0666|IPC_CREAT);
- if(shmid == -1)
- {
- fprintf(stderr, "shmget failed\n");
- exit(EXIT_FAILURE);
- }
- //将共享内存连接到当前进程的地址空间
- shm = shmat(shmid, (void*)0, 0);
- if(shm == (void*)-1)
- {
- fprintf(stderr, "shmat failed\n");
- exit(EXIT_FAILURE);
- }
- printf("Memory attached at %X\n", (int)shm);
- //设置共享内存
- shared = (struct shared_use_st*)shm;
- while(running)//向共享内存中写数据
- {
- //数据还没有被读取,则等待数据被读取,不能向共享内存中写入文本
- while(shared->written == 1)
- {
- sleep(1);
- printf("Waiting...\n");
- }
- //向共享内存中写入数据
- printf("Enter some text: ");
- fgets(buffer, BUFSIZ, stdin);
- strncpy(shared->text, buffer, TEXT_SZ);
- //写完数据,设置written使共享内存段可读
- shared->written = 1;
- //输入了end,退出循环(程序)
- if(strncmp(buffer, "end", 3) == 0)
- running = 0;
- }
- //把共享内存从当前进程中分离
- if(shmdt(shm) == -1)
- {
- fprintf(stderr, "shmdt failed\n");
- exit(EXIT_FAILURE);
- }
- sleep(2);
- exit(EXIT_SUCCESS);
- }
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