#Trying to share memory between 2 C files

9 messages · Page 1 of 1 (latest)

raven sun
#

Hello. I am trying to share memory between two C programs. Right now my program creates the log file, but no text is appended. I am extremely new to C programming so any help is appreciated.

quaint birchBOT
#

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raven sun
# 
#include<sys/ipc.h>
#include<sys/shm.h>
#include<sys/types.h>
#include<string.h>
#include<errno.h>
#include<stdlib.h>
#include<unistd.h>
#include<string.h>

#define BUF_SIZE 1024
#define SHM_KEY 0x1234

struct shmseg {
   int cnt;
   int new;
   int complete;
   char buf[BUF_SIZE];
};


int main(int argc, char *argv[]) {

   int shmid, numtimes;
   struct shmseg *shmp;
   char *bufptr;
   int spaceavailable;
   shmid = shmget(SHM_KEY, sizeof(struct shmseg), 0666|IPC_CREAT);
   if (shmid == -1) {
      perror("Shared memory");
      return 1;
   }
   
   // Attach to the segment to get a pointer to it.
   shmp = shmat(shmid, NULL, 0);
   if (shmp == (void *) -1) {
      perror("Shared memory attach");
      return 1;
   }
   

   /***********************************************************
    *  write code here to contiuesly get message from user so the logserver can log the information to log file
    * unless user give the input to quit the process. 
    * ********************************************************/
    do{
        
      printf("Type in something. type quit to exit the program: ");

      scanf("%s", shmp->buf);
      

      shmp->new = 1;

      numtimes++;

    } while (strcmp(shmp->buf, "quit") != 0);
    

   printf("Writing Process: Wrote %d times\n", numtimes);



   /*****************************************************************
   this is code to quit the process, and terminate the logserver program
   ***********************************************************************/

   shmp->complete = 1;

  /*************************************************************
  write the code to detach the share memory from the process
  *******************************************************/

   if (shmdt(shmp) == -1) {
      perror("shmdt");
      return 1;
   }


   printf("Writing Process: Complete\n");
   return 0;
}```
#

thats the first file. its the log client file

#

This is the second file:

#include<sys/ipc.h>
#include<sys/shm.h>
#include<sys/types.h>
#include<string.h>
#include<errno.h>
#include<stdlib.h>

#define BUF_SIZE 1024
#define SHM_KEY 0x1234

struct shmseg {
   int cnt;
   int new;
   int complete;
   char buf[BUF_SIZE];

   
};

int main(int argc, char *argv[]) {
   int shmid;
   struct shmseg *shmp;

   FILE *file_e3;

   file_e3 = fopen("log_file.log", "a+");

   if (file_e3 == NULL) {
   perror("Error");
   return 1;
   }

   shmid = shmget(SHM_KEY, sizeof(struct shmseg), 0666|IPC_CREAT);
   if (shmid == -1) {
      perror("Shared memory");
      return 1;
   }
   
   // Attach to the segment to get a pointer to it.
   shmp = shmat(shmid, NULL, 0);
   if (shmp == (void *) -1) {
      perror("Shared memory attach");
      return 1;
   }
   
   /* Transfer blocks of data from shared memory to log file 
   if the message from client set shmp->complete ==1, the we log server will end its operation 
   if the message from the client is new, then the message should be log in the log file 

   */

   while(shmp->complete != 1)
   {
        while (shmp->new == 1) {

         fwrite(shmp->buf, sizeof(char), strlen(shmp->buf), file_e3);



            
          // after the message send to file,  put the shmp->new to false
          shmp->new = 0;   
        }
   }


   fclose(file_e3);
  /*************************************************************
  write the code to detach the share memory from the process
  *******************************************************/
    if (shmdt(shmp) == -1) {
        perror("shmdt");
        return 1;
    }
   


   /*********************************************************
   write the code to mark the shared memory to be destroyed
   *********************************************************/
    if (shmctl(shmid, IPC_RMID, NULL) == -1) {
        perror("shmctl");
        return 1;
    }  



   return 0;
}```
#

this is the server part

fathom peak
#

Nah, it is working. You probably won't see any log file contents unless the client types 'quit' and closes the file. You could to a fflush after every fwrite and then you would see it.

raven sun
#

!solved