如何实现流程方面的互斥锁和条件变量

Question

我有两个进程在运行。一个是主服务器，另一个是代理服务器。它们都通过共享内存进行通信。代理服务器写入文件的名称，mainserver读取它。然后主服务器写入要由代理服务器读取的该文件的内容。以下是代码： 主服务器：

   //receive data from client  
       memset(&buffer,'\0',sizeof(buffer));  
       bytes = read(c_fd, buffer, sizeof(buffer)); 
       if(!(bytes<0 && bytes==0 )){ 


  //SHARED MEMORY STUFF :) //

  for(int i=0; i<strlen(b);i++)
        printf("%c", b[i]);
  char c;
  int shmid;
  key_t key;
  char *shm;
  char *s= (char *)malloc (strlen(buffer)+1);
  //naming shared memory segment 5678
  key=5678;
  //Locate the segment
  if((shmid =shmget (key,SHMSZ,0666))<0){
       perror("shmget");
       exit(1);
 }
  //attaching the segment
 if((shm =shmat (shmid,NULL,0))==(char *) -1){
       perror("shmat");
       exit(1);

 }
 int count=0;
 s =shm;
 printf("File name received is :\n");

 for(s=shm ; *s!=NULL; s++){

       putchar (*s);
       if((*s >='a'    &&  *s<='z'  )  || *s=='.' ){

           b[count]=*s;
           count++;}
      // else printf("special character");




 }

// *shm = '*';
 //*s=NULL;
 //shmdt ((void *)shmid);

 //reading html file

  printf("coiunt%d",count);
  char *ss="page2.html"; 
  printf("%s",b);    
  char shared_buffer[69999]; 
  int handle = open(b, O_RDONLY);
     if (handle!=-1)    //FILE FOUND// change
        {
            printf("inside %s",b);

            send(c_fd, "File found\n\n", 17, 0);
                                //reading html file
                                if(read(handle, shared_buffer, 1024)!=-1)
                                         printf("READ");
                                //adding data to segment
                                //printf("sharedddd %c",shared_buffer[0]);
                        s= shm;

                                for(int i=0; i<strlen(shared_buffer); i++){
                                *s++= shared_buffer[i];
                                printf(" %s",s);
                               // printf("sharedddd %c",shared_buffer[i]);
                                }
                                *s= NULL;


            }
        else    {//write(c_fd, " Not Found\n", 23); //FILE NOT FOUND
                                }





  }



         fflush(stdout);  


 }

代理服务器：

           //receive data from client  
           memset(&buffer,'\0',sizeof(buffer));  
           bytes = read(c_fd, buffer, sizeof(buffer)); 
           if(!(bytes<0 && bytes==0 )){ 


          //SHARED MEMORY STUFF :) //

          for(int i=0; i<strlen(b);i++)
                printf("%c", b[i]);
          char c;
          int shmid;
          key_t key;
          char *shm;
          char *s= (char *)malloc (strlen(buffer)+1);
          //naming shared memory segment 5678
          key=5678;
          //Locate the segment
          if((shmid =shmget (key,SHMSZ,0666))<0){
               perror("shmget");
               exit(1);
         }
          //attaching the segment
         if((shm =shmat (shmid,NULL,0))==(char *) -1){
               perror("shmat");
               exit(1);

         }
         int count=0;
         s =shm;
         printf("File name received is :\n");

         for(s=shm ; *s!=NULL; s++){

               putchar (*s);
               if((*s >='a'    &&  *s<='z'  )  || *s=='.' ){

                   b[count]=*s;
                   count++;}
              // else printf("special character");




         }

        // *shm = '*';
         //*s=NULL;
         //shmdt ((void *)shmid);

         //reading html file

          printf("coiunt%d",count);
          char *ss="page2.html"; 
          printf("%s",b);    
          char shared_buffer[69999]; 
          int handle = open(b, O_RDONLY);
             if (handle!=-1)    //FILE FOUND// change
                {
                    printf("inside %s",b);

                    send(c_fd, "File found\n\n", 17, 0);
                                        //reading html file
                                        if(read(handle, shared_buffer, 1024)!=-1)
                                                 printf("READ");
                                        //adding data to segment
                                        //printf("sharedddd %c",shared_buffer[0]);
                                s= shm;

                                        for(int i=0; i<strlen(shared_buffer); i++){
                                        *s++= shared_buffer[i];
                                        printf(" %s",s);
                                       // printf("sharedddd %c",shared_buffer[i]);
                                        }
                                        *s= NULL;


                    }
                else    {//write(c_fd, " Not Found\n", 23); //FILE NOT FOUND
                                        }





          } 
             fflush(stdout);  

 }  

我只添加了创建和共享内存的相关代码。请注意，这两个代码都在单独的文件中。我需要实现互斥和条件变量，这样当主服务器只能在代理服务器写入内存后才能读取，依此类推。我在互联网上搜索过代码，但它们似乎都在为一个文件工作。如何在两个文件之间共享？请告知一些教程或任何让我入门的内容。