errno()

A global variable for storing error result.

  #include <errno.h> 
  extern int errno;

Remarks

Many functions in the standard library return a special value when an error occurs. Often the programmer needs to know about the nature of the error. Some functions provide more detailed error information by assigning a value to the global variable errno. A value of zero specifies that there is no error. A non-zero value specifies that a function encountered an error.

An EWL function only assigns a value to errno when an error occurs. It is the programmer's responsibility to assign 0 to errno before calling a function that uses it.

The table below lists the values that EWL functions use to report an error condition.

Table 1. EWL Date and Time Management Macros
Error Code	Description
`EDOM`	A numerical argument is not within the acceptable range of values that a function requires.
`EILSEQ`	An operation to convert to or from a multibyte character sequence could not be completed.
`ERANGE`	A result could not be computed because it would be beyond the range of values that can be stored in its data type.

Listing: Example of errno() Usage


#include <errno.h> 
#include <stdio.h> 
#include <extras.h> 
int main(void) 
{ 
char *num = "999999999999999999999999999999999"; 
long result; 
errno = 0; /* Assume no error. */ 
result = strtol( num, 0, 10); 
if (errno == 0) 
printf("The string as a long is %ld", result); 
else 
printf("Conversion error\n"); 
return 0; 
} 
Output: 
Conversion error