Thread: help with read()

Hi all, I'm trying to read a misc device /dev/pi

When I do "cat /dev/pi" I get my desired output. However, I'm trying to test with the following code and running into problems.

Code:

#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>


char buffer[10];

int main()
{

  int test = open("/dev/pi", O_RDWR);
  if (test < 0)
    printf ("Couldn't open file\n");
  else
    printf("File Opened Successfully\n");


  int test2 = read(test,*buffer,sizeof(buffer));

  printf("The fd is: %i\n", test);

  printf("Output from read function: %i\n", test2);

  printf("Pi: %s", buffer);

}

Seems to open the file successfully but it doesn't read the file correctly. This is the output:

File Opened Successfully
The fd is: 3
Output from read function: -1
Pi:

Any help?

int test2 = read(test,*buffer,sizeof(buffer));

I believe read requires the address of the buffer. Since you defined it as a char array, its address would be simply buffer.

Code:

int test2 = read(test,buffer,sizeof(buffer));