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所有函数所需的头文件请用man手册查阅，这里都不写了
使用共享内存步骤:
① 开辟一块共享内存shmget
② 允许本进程使用共某块共享内存shmat
③ 写入/读取
删除共享内存步骤
①禁止本进程使用这块共享内存shmdt
②删除这块共享内存shmctl或者命令行下ipcrm
1、创建共享内存
任务描述：
相关知识：
共享内存函数由 shmget、shmat、shmdt、shmctl 四个函数组成。
①shmget函数
作用：得到一个共享内存标识符或创建一个共享内存对象
原型：int shmget(key_t key, size_t size, int shmflg)
②shamat函数
作用：连接共享内存标识符为 shmid 的共享内存,连接成功后把共享内存区对象映射到调用进程的地址空间,随后可像本地空间一样访问
原型：void *shmat(int shmid, const void *shmaddr, int shmflg)
③shmdt函数
作用：断开与共享内存附加点的地址,禁止本进程访问此片共享内存
原型：int shmdt(const void *shmaddr)
④shmctl函数
作用:完成对共享内存的控制
原型：int shmctl(int shmid, int cmd, struct shmid_ds *buf)
main.c:
#include<stdio.h> #include<stdlib.h> #include<unistd.h> #include<sys/ipc.h> #include<sys/shm.h> #include<error.h> #include<string.h> int main(void) { int shmid;char x[10]; struct shmid_ds buf; char *shmaddr; shmid=shmget(IPC_PRIVATE,512,IPC_CREAT|0600 ) ; if ( shmid < 0 ){ perror("get shm ipc_id error\n") ; return -1 ; } //printf("shmid is %d\n",shmid); pid_t pid; pid=fork(); if(pid<0){ perror("fork error\n"); shmctl(shmid,IPC_RMID,&buf); } if(pid==0){ //printf("this is child\n"); //printf("child pid is %d\n",getpid()); shmaddr=(char *)shmat(shmid,NULL,0); if(shmaddr<(char *)0){ perror("shmat addr error\n"); return -1; } printf("write something to shm\n"); fgets(x,11,stdin); strcpy(shmaddr,x); shmdt(shmaddr); return 0; }else{ //memset(&buf,‘\0‘,sizeof(buf)); wait(); shmctl(shmid,IPC_STAT,&buf); printf("The size of new buf is %ld bytes\n",buf.shm_segsz); shmaddr=(char *)shmat(shmid,NULL,0); printf("your input string is :%s\n",shmaddr); } return 0 ; }
2、使用fork函数创建子进程
任务描述:
main.c:
#include <stdio.h> #include <unistd.h> #include <sys/ipc.h> #include <sys/shm.h> #include <error.h> int main(void) { int shmid; struct shmid_ds buf; shmid=shmget(IPC_PRIVATE,512,IPC_CREAT|0600 ) ; if ( shmid < 0 ){ perror("get shm ipc_id error") ; return -1 ; } printf("shmid is %d\n",shmid); pid_t pid; pid=fork(); if(pid<0){ perror("fork error\n"); shmctl(shmid,IPC_RMID,&buf); } if(pid==0) printf("this is child\n"); else printf("this is parent\n"); return 0 ; }
3、在子进程中将键盘输入字符串写入共享内存
任务描述:
main.c:
#include<stdio.h> #include<stdlib.h> #include<unistd.h> #include<sys/ipc.h> #include<sys/shm.h> #include<error.h> #include<string.h> int main(void) { int shmid;char x[10]; struct shmid_ds buf; char *shmaddr; shmid=shmget(IPC_PRIVATE,512,IPC_CREAT|0600 ) ; if ( shmid < 0 ){ perror("get shm ipc_id error\n") ; return -1 ; } printf("shmid is %d\n",shmid); pid_t pid; pid=fork(); if(pid<0){ perror("fork error\n"); shmctl(shmid,IPC_RMID,&buf); } if(pid==0){ printf("this is child\n"); shmaddr=(char *)shmat(shmid,NULL,0); if(shmaddr<(char *)0){ perror("shmat addr error\n"); return -1; } printf("write something to shm\n"); fgets(x,11,stdin); strcpy(shmaddr,x); // printf("%s\n",shmaddr); shmdt(shmaddr); return 0; }else{ wait(); printf("this is parent\n"); shmaddr=(char *)shmat(shmid,NULL,0); printf("%s\n",shmaddr); } return 0 ; }
4、打印共享内存大小和子进程、父进程进程号
任务描述：
main.c：
#include<stdio.h> #include<stdlib.h> #include<unistd.h> #include<sys/ipc.h> #include<sys/shm.h> #include<error.h> #include<string.h> int main(void) { int shmid;char x[10]; struct shmid_ds buf; char *shmaddr; shmid=shmget(IPC_PRIVATE,512,IPC_CREAT|0600 ) ; if ( shmid < 0 ){ perror("get shm ipc_id error\n") ; return -1 ; } //printf("shmid is %d\n",shmid); pid_t pid; pid=fork(); if(pid<0){ perror("fork error\n"); shmctl(shmid,IPC_RMID,&buf); } if(pid==0){ printf("this is child\n"); printf("child pid is %d\n",getpid()); //shmaddr=(char *)shmat(shmid,NULL,0); // if(shmaddr<(char *)0) // { // perror("shmat addr error\n"); //return -1; //} //printf("write something to shm\n"); //fgets(x,11,stdin); //strcpy(shmaddr,"your input string is‘xxx‘\n"); //shmdt(shmaddr); return 0; } else{ //memset(&buf,‘\0‘,sizeof(buf)); //wait(); //printf("%s\n",shmaddr); shmctl(shmid,IPC_STAT,&buf); printf("The size of new buf is %ld bytes\n",buf.shm_segsz); printf("this is parent\n"); printf("parent pid is %d\n",getpid()); } return 0 ; }
5、两个进程通过共享内存通信
任务描述:
写程序:
write.c:
#include<stdio.h> #include<stdlib.h> #include<unistd.h> #include<sys/ipc.h> #include<sys/shm.h> #include<error.h> #include<string.h> #include<sys/types.h> typedef struct book { int num; char name[20]; float price; }book; int main(void) { int shmid,i; key_t key; book *shmaddr; char temp[20]; key=ftok("write.c",0x03); if(key==-1){ perror("key error\n"); return -1; } printf("key=%d\n",key); shmid=shmget(key,512,IPC_CREAT|0600 ) ; if (shmid<0){ perror("shmid get error\n") ; return -1 ; } else{ printf("shmid =%d\n",shmid); shmaddr=(book *)shmat(shmid,NULL,0); if(shmaddr<(book *)0){ perror("shmat addr error\n"); return -1; } memset(temp,0x00,sizeof(temp)); strcpy(temp,"book"); temp[4]=‘0‘; for(i=0;i<2;i++){ temp[4]+=1; strcpy((shmaddr+i) -> name,temp); (shmaddr+i) -> num=i; (shmaddr+i)->price=10*(i+1); } shmdt(shmaddr); } return 0 ; }
读程序:
read.c:
#include<stdio.h> #include<stdlib.h> #include<unistd.h> #include<sys/ipc.h> #include<sys/shm.h> #include<error.h> #include<string.h> #include<sys/types.h> typedef struct book { int num; char name[20]; float price; }book; int main(void) { int shmid,i; char temp[20]; key_t key; book *shmaddr; key=ftok("write.c",0x03); if(key==-1){ perror("key error\n"); return -1; } printf("key=%d\n",key); shmid=shmget(key,512,IPC_CREAT|0600 ) ; if (shmid<0){ perror("shmid get error\n") ; return -1 ; } else{ printf("shmid =%d\n",shmid); shmaddr=(book *)shmat(shmid,NULL,0); if(shmaddr<(book *)0){ perror("shmat addr error\n"); return -1; } for(i=0;i<2;i++){ printf("num:%d,",(*(shmaddr+i)).num); printf("name:%s,",(*(shmaddr+i)).name); printf("price:%f\n",(*(shmaddr+i)).price); } shmdt(shmaddr); } return 0 ; }
6、无名管道
任务描述:
main.c:
#include <unistd.h> #include <stdio.h> #define size 100 int main(void) { int filedes[2]; char a[size],b[size]; pid_t pid; pipe(filedes); pid=fork(); if(pid<0){ printf("pid error\n"); return 0; } if (pid > 0){ printf( "This is father process\n"); printf("please input something and wait a little time\n"); fgets(a,50,stdin); printf("write pipe:%s\n",a); write( filedes[1],a,sizeof(a)); close( filedes[0] ); close( filedes[1] ); } else if(pid == 0){ sleep(7); printf("This is child process.\n"); read( filedes[0], b, sizeof(b)); printf( "read pipe: %s\n", b ); close( filedes[0] ); close( filedes[1] ); } waitpid( pid, NULL, 0 ); return 0; }
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原文地址：http://www.cnblogs.com/weijing24/p/4761808.html
