#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <errno.h>

int main(void) {
  double input = -1.0, x = 0.0;

  /* Take square root of a negative number, prepare for error reporting */ 
  errno = 0;         /* Reset errno */

  x = sqrt(input);   /* sqrt assigns errno in case of error */

  if (errno){  /* errno is positive in case of an error */
     printf("sqrt failed, code: %d, message: '%s'\n", errno, strerror(errno));
     x = 0.0;
  }
  printf("Result is %f\n", x);

  return 0;
}