Question

How to print the errno value and the error messages (error handling) in C

Answer 1

#include <stdio.h>
#include <string.h>
#include <errno.h>
 
int main()
{
    FILE *fp;
  
    // 2 - No such file or directory 
    fp = fopen("d:\\data-----txt", "r");
  
    printf("errno: %d\n", errno);
    printf("error message: %s\n", strerror(errno));
    
    return 0;
}



 
/*
run:
   
errno: 2
error message: No such file or directory
  
*/

 

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Answer 2

#include <stdio.h>
#include <math.h>
#include <errno.h>
#include <string.h>
 
int main(void)
{
    errno = 0;
    printf("log(-1.0) = %f\n", log(-1.0));
    printf("errno: %d\n", errno);
    printf("error message: %s\n", strerror(errno));

    errno = 0;
    printf("log(0.0)  = %f\n", log(0.0));
    printf("errno: %d\n", errno);
    printf("error message: %s\n", strerror(errno));
}

  
  
  
/*
run:
  
log(-1.0) = -nan
errno: 33
error message: Numerical argument out of domain
log(0.0)  = -inf
errno: 34
error message: Numerical result out of range
  
*/

 

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