C指针原理（91)-LINUX应用(3)-进程写文件,另一进程读输入

线程池共享内存+信号量

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$myhaspl
 
deepfuture.javeye.com#line 5$Q
 
deepfuture.javeye.com#line 6$
退出....
deepfuture@deepfuture-laptop:~/private/mytest$ cat abc.txt
deepfuture
javaeye
com
myhaspl
deepfuture@deepfuture-laptop:~/private/mytest$ 

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http://blog.csdn.net/myhaspl/

C代码  
#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。  
//myhaspl  
  
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 myhaspl   
    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 myhaspl   
    shm_addr=(char *)shmat(shm_id,NULL,0);//返回共享内存地址 myhaspl   
    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 myhaspl   
         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 myhaspl                      
               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    myhaspl          
            
          while(1)  
          {  
            //读出一行，减少信号  myhaspl   
              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     
              
              //myhaspl  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);//myhaspl  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。myhaspl   
              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);   
         }  
}