Question

LINUX 信号量共存 共享内存通信

编写两个程序Mysem.c(编译后为mysem)和Msginput.c（编译后为msginput）,实现两个程序（进程）之间的通信。要求如下：
1、 mysem创建一个共享内存myshm(共享内存ID，内存大小为512字节)，供mysem和myinput共享
2、 mysem创建一个子进程，该子进程加载myinput
3、 myinput从键盘以追加方式向myshm中输入信息（字符型），mysem接收信息并显示在屏幕上
4、 当myinput从键盘输入“end”并存入myshm后，myinput结束（退出），mysem收到“end”显示后，也退出，并释放所有的资源。

要运用到信号量的PV操作。
需要的效果是：输入一条，接收一条，打入END后,myinput退出，mysem输出END后也退出。

本人非常急，高分求答案。我要两个程序的源代码，若运行通过且在明早7点前，可加分。谢谢

Answer 1

/***Msginput.c***/
#include<sys/types.h>
#include<sys/ipc.h>
#include<sys/shm.h>
#include<sys/sem.h>
#include<unistd.h>
#include<stdio.h>
#include<errno.h>
#include<string.h>
#include"Mysem.h"

int main(){
FILE *fp;
int empty;
int full;
int mutex;
char * shm;
int shmid;
fp = fopen("shmid","r");
fread(&shmid,sizeof(int), 1, fp);
fread(&empty,sizeof(int), 1, fp);
fread(&full,sizeof(int), 1, fp);
fread(&mutex,sizeof(int), 1, fp);

fclose(fp);
shm = shmat(shmid, NULL, 0);

while(1){

P(&empty);
P(&mutex);

scanf("%s", shm);

if(strcmp(shm, "END") == 0){

V(&mutex);
V(&full);
break;
}

V(&mutex);
V(&full);

}
return 0;
}

/****Mysem.c*****/
#include<sys/types.h>

#include<sys/ipc.h>

#include<sys/shm.h>

#include<sys/sem.h>

#include<unistd.h>

#include<stdio.h>

#include<errno.h>

#include<string.h>

#include "Mysem.h"

#define BUFFER_SIZE 512

int main(){

char *shm;

int empty;

int full;

int mutex;

int shmid;

int pid;

int i;

FILE *fp;

// int init_sem_value = 0;

empty = semget(IPC_PRIVATE, 1, (0600|IPC_CREAT));

if(empty == -1){

perror("semget");

exit(1);

}

if(semctl(empty, 0, SETVAL, 1)<0){

perror("semctl");

exit(1);

}

full = semget(IPC_PRIVATE, 1, (0600|IPC_CREAT));

if(full == -1){

perror("semget");

exit(1);

}

if(semctl(full, 0, SETVAL, 0)<0){

perror("semctl");

exit(1);

}

mutex = semget(IPC_PRIVATE, 1, (0600|IPC_CREAT));

if(mutex == -1){

perror("semget");

exit(1);

}

if(semctl(mutex, 0, SETVAL, 1)<0){

perror("semctl");

exit(1);

}

shmid = shmget(IPC_PRIVATE, (BUFFER_SIZE*sizeof(char)),(IPC_CREAT|0600));

if(shmid == -1){

perror("shmget");

exit(1);

}

shm = shmat(shmid, NULL, 0);

if(shm == (char*)-1){

perror("shmat");

exit(1);

}

fp = fopen("shmid","w");

fwrite(&shmid, sizeof(int), 1, fp);

fwrite(&empty, sizeof(int), 1, fp);

fwrite(&full, sizeof(int), 1, fp);

fwrite(&mutex, sizeof(int), 1, fp);

fclose(fp);

pid = fork();

if(pid == 0){

execlp("./Msginput", "./Msginput",0);

perror("execlp");

exit(1);

}else{

while(1){

P(&full);

P(&mutex);

printf("%s\n", shm);

if(strcmp(shm,"END") == 0){

V(&mutex);

V(&empty);

break;

}

V(&mutex);

V(&empty);

}

}

wait(0);

if(semctl(full, 0, IPC_RMID, 1) == -1){

perror("semctl");

exit(1);

}

if(semctl(empty, 0, IPC_RMID, 1) == -1){

perror("semctl");

exit(1);

}

if(semctl(mutex, 0, IPC_RMID, 1) == -1){

perror("semctl");

exit(1);

}

if(shmctl(shmid, IPC_RMID, NULL) == -1){

perror("shmctl");

exit(1);

}

exit(0);

}

/****Mysem.h*****/
void P(int *s);
void V(int *s);

extern void *shmat (int __shmid, __const void *__shmaddr, int __shmflg);

void P(int *s){
struct sembuf sembuffer, *sops;
sops=&sembuffer;
sops->sem_num = 0;
sops->sem_op = -1;
sops->sem_flg = 0;
if(semop(*s, sops, 1)<0){
perror("semop");
exit(1);
}
return ;
}
void V(int *s){
struct sembuf sembuffer, *sops;
sops = &sembuffer;
sops->sem_num = 0;
sops->sem_op = 1;
sops->sem_flg = 0;
if(semop(*s, sops, 1)<0){
perror("semop");
exit(1);
}
return;
}