read write to file

Hi,
How can I erase the data stored in /tmp/a.txt after every run of this code?

Code:

#include <stdio.h>      // IO operations
#include <unistd.h>       //for pid, ppid, fork functions
#include <sys/types.h>  //for pid_t type, kill function
#include <stdlib.h>     //for exit function
#include <signal.h>    //for kill function
#include <sys/types.h>
#include <sys/stat.h>
#include <string.h>
#include <fcntl.h>
#include <unistd.h>
#include <assert.h>
#include <error.h>

int main()
{
 int fd;
 pid_t x=fork();
 char bufferSize[80];
 char buffer[]="Wellcome to Linux Embedded";
 char bufferNull[]=" ";
 fd=open("/tmp/a.txt", O_RDWR | O_CREAT ,0777);
 //printf("fd=%d\n",fd);
 if(fd==-1)
 {
 printf("can't open file\n");
 }
 
 if(x>0)
 {
    read (fd, bufferSize, sizeof(bufferSize));
    printf("reading to file\n");
  
   write (fd, buffer, strlen(buffer));
   printf("writing to file\n");
   
 }

 close (fd) ;// Close the file descriptor
 return 0;
 }

If you want to physically remove the file from storage:
remove - Stdio.h - C - C++ Computing Reference with Worked Examples

If you want to delete the contents, you can overwrite it with this:

Code:

FILE *file;
if ((file = fopen("/tmp/a.txt", "w")) != NULL) 
  fclose(file);

I really don't know how that translates to file descriptors. That is a pretty old API, are you sure you need to use it?

If you need a temporary file I suggest using tmpfile(). After closing the file or exiting the program, the file will be removed automatically.

Bye, Andreas

thanks