linux-C-共享内存+信号量-一进程写文件,另一进程读输入

deepfuture@deepfuture-laptop:~/private/mytest$ gcc -std=gnu99 -o testshm testshm.c

testshm.c: In function ‘main’:

testshm.c:38: warning: implicit declaration of function ‘semget’

testshm.c:41: warning: implicit declaration of function ‘exit’

testshm.c:41: warning: incompatible implicit declaration of built-in function ‘exit’

testshm.c:45: warning: implicit declaration of function ‘semctl’

testshm.c:48: warning: incompatible implicit declaration of built-in function ‘exit’

testshm.c:51: warning: implicit declaration of function ‘shmget’

testshm.c:54: warning: incompatible implicit declaration of built-in function ‘exit’

testshm.c:57: warning: implicit declaration of function ‘shmat’

testshm.c:60: warning: incompatible implicit declaration of built-in function ‘exit’

testshm.c:63: warning: implicit declaration of function ‘memset’

testshm.c:63: warning: incompatible implicit declaration of built-in function ‘memset’

testshm.c:69: warning: incompatible implicit declaration of built-in function ‘exit’

testshm.c:78: warning: implicit declaration of function ‘strlen’

testshm.c:78: warning: incompatible implicit declaration of built-in function ‘strlen’

testshm.c:85: warning: implicit declaration of function ‘memcpy’

testshm.c:85: warning: incompatible implicit declaration of built-in function ‘memcpy’

testshm.c:92: warning: implicit declaration of function ‘semop’

testshm.c:95: warning: incompatible implicit declaration of built-in function ‘exit’

testshm.c:119: warning: incompatible implicit declaration of built-in function ‘strlen’

testshm.c:124: warning: incompatible implicit declaration of built-in function ‘exit’

testshm.c:132: warning: implicit declaration of function ‘wait’

testshm.c:134: warning: implicit declaration of function ‘shmdt’

testshm.c:139: warning: implicit declaration of function ‘shmctl’

testshm.c:142: warning: incompatible implicit declaration of built-in function ‘exit’

deepfuture@deepfuture-laptop:~/private/mytest$ ./testshm

 

deepfuture.javeye.com#line 1$deepfuture

 

deepfuture.javeye.com#line 2$javaeye

 

deepfuture.javeye.com#line 3$com

 

deepfuture.javeye.com#line 4$deepfuture.iteye.com

 

deepfuture.javeye.com#line 5$Q

 

deepfuture.javeye.com#line 6$

退出....

deepfuture@deepfuture-laptop:~/private/mytest$ cat abc.txt

deepfuture

javaeye

com

deepfuture.iteye.com

deepfuture@deepfuture-laptop:~/private/mytest$ 

#include <stdio.h>
#include <unistd.h>
#include <linux/types.h>
#include <linux/shm.h>
#include <linux/sem.h>
#include <linux/ipc.h>




#define MAXS  (1024+1)
#define BUFFERSIZE  200
#define SEMID 251//信号标志
#define FILENAME "abc.txt"
#define SHMKEY 241//共享内存标志
#define SHMSIZE MAXS//共享内存大小


//程序完成父进程接收键盘输入，子进程存入文件FILENAME。
//deepfuture.iteye.com

int main(void){
    char strbuf[MAXS];
    char buf[BUFFERSIZE];
    int sem_id;
    int shm_id;
    int pid;
    int rc,res;
    struct sembuf sem_op;//信号集结构
    union semun sem_val;//信号量数值
    char *cur;
    FILE *myfile;
    char *shm_addr;
    int line=1;

    
    //建立信号量集，其中只有一个信号量 deepfuture.iteye.com 
    sem_id=semget(SEMID,1,IPC_CREAT|0600);//SEMID为为正整数，则为公共的；1为信号集的数量；
    if (sem_id==-1){
        printf("create sem error!\n");
        exit(1);    
    }
    //信号量初始化
    sem_val.val=0;
    rc=semctl(sem_id,0,SETVAL,sem_val);//设置信号量
    if (rc==-1){
        printf("initlize sem error!\n");
        exit(1);    
    }
    //建立共享内存
    shm_id=shmget(SHMKEY,SHMSIZE,IPC_CREAT|0600);//参数为:标志，大小，权限
    if (shm_id==-1){
        printf("create shm error!\n");
        exit(1);    
    }     
    //attach共享内存。连接共享内存 deepfuture.iteye.com 
    shm_addr=(char *)shmat(shm_id,NULL,0);//返回共享内存地址 deepfuture.iteye.com 
    if (!shm_addr){
        printf("shmat error!\n");
        exit(1);    
    } 
    //初始化数据
    memset(shm_addr,'\0',MAXS);  
    cur=shm_addr;//当前字符起始地址
    //创建进程
    pid=fork();
    if (pid==-1){
        printf("fork error!\n");
        exit(1);           
    }
    else if(pid==0){//子进程，接受键盘输入，往共享内存中写字符行 deepfuture.iteye.com 
         int isend=0;//是否结束输入
 	  	 printf("\ndeepfuture.javeye.com#line %d$",line); //自定义键盘输入时使用的SHELL外观   
         while((!isend)&&fgets(buf,BUFFERSIZE,stdin)!=NULL){//从shell中读入一行  
             line++;       
 	  	     printf("\ndeepfuture.javeye.com#line %d$",line); //自定义键盘输入时使用的SHELL外观 	 
 	  	       
             if (buf[0]=='Q'&&strlen(buf)<=2){//单个字符Q表示退出输入
                 isend++;//退出输入
                 printf("\n退出....\n");
             }
             else
             {//如果不是退出命令             	  	   
    	  	   //写共享内存 deepfuture.iteye.com 	      	  	   
        	   memcpy(cur,buf,strlen(buf)); 	  	   
    	  	   cur+=strlen(buf);
    	  	 }  
    	  	   //写入一行，增加信号
               sem_op.sem_num=0;
               sem_op.sem_op=1;
               sem_op.sem_flg=0;
               semop(sem_id,&sem_op,1);//操作信号量，每次+1 	   
	  	  } 
 	      *cur=-1; 
 	  	  exit(0);   
    }
    else{//父进程，从共享内存中读字符行 ,并写入文件    deepfuture.iteye.com 	    
       	  
          while(1)
          {
            //读出一行，减少信号  deepfuture.iteye.com 
              sem_op.sem_num=0;
              sem_op.sem_op=-1;
              sem_op.sem_flg=0;
              semop(sem_id,&sem_op,1);//操作信号量，每次-1   
            
        	  //deepfuture.iteye.com  读共享内存中一行
        	 if ((*cur)==-1) break;//输入结束
             int i;
        	      for (i=0;*cur!='\n';cur++,i++){      	        
            	        buf[i]=*cur;   	        
        	      }   
        	  cur++;        	      
          	  buf[i]='\n';
        	  buf[++i]=0;
       	  
        	  //写文件
              FILE *fp=fopen(FILENAME,"ab");
        	  res=fwrite(buf,strlen(buf),1,fp);//deepfuture.iteye.com  写入一个行，长度为strlen(buf)，个数为1     	  
        	  //size_t fwrite(const void * ptr,size_t size,size_t nmemb,FILE * stream);
        	  //size为要写入的每个数据的大小(多少字节)，nmemb为要写入数据的个数。deepfuture.iteye.com 
              if (res==-1){   
                  perror("write error on pipe\n");   
                  exit(1);                   
              } 
              fclose(fp);  
                      	
          }

        	          
  	  
 	  	  wait(&pid);//等待子进程结束，即用户输入完毕
 	  	  //分离共享进程
 	  	  if (shmdt(shm_addr)==-1){
              printf("shmdt error!\n"); 	  	      
 	  	  }
 	  	  //撤销共享内存,任何进程只要有权限，都可以撤销共享内存，不一定非要创建它的进程
 	  	  struct shmid_ds shm_desc;
 	  	  if (shmctl(shm_id,IPC_RMID,&shm_desc)==-1){
 	  	      printf("shmctl error!\n");
 	  	  }
 	  	  exit(0); 
 	  	 }
}