Cape on my BBB in .c File Format

#include <fcntl.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>

int main()
{
  int fd = open( "/sys/class/gpio/gpio20/value", O_RDWR | O_CLOEXEC );
  if( fd < 0 ) {
    fprintf( stderr, "open: %m\n" );
    exit(1);
  }

  char c = '0';
  write( fd, &c, 1 );
  close( fd );

  return 0;
}