Error numbers

< c‎ | error

Each of the macros defined in <errno.h> expands to an integer constant expression with type int and with a unique positive value. The following constants are defined (the implementation may define more, as long as they begin with 'E' followed by digits or uppercase letters)

Defined in header <errno.h>
Mathematics argument out of domain of function
(macro constant)
Illegal byte sequence
(macro constant)
Result too large
(macro constant)


[edit] Notes

Many additional errno constants are defined by POSIX and by the C++ standard library, and individual implementations may define even more, e.g. errno(3) on Linux or intro(2) on BSD and OS X.

[edit] Example

#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));
    errno = 0;
    printf("log(0.0)  = %f\n", log(0.0));

Possible output:

log(-1.0) = nan
Numerical argument out of domain
log(0.0)  = -inf
Numerical result out of range

[edit] References

  • C11 standard (ISO/IEC 9899:2011):
  • 7.5/2 Errors <errno.h> (p: 205)
  • C99 standard (ISO/IEC 9899:1999):
  • 7.5/2 Errors <errno.h> (p: 186)
  • C89/C90 standard (ISO/IEC 9899:1990):
  • 4.1.3 Errors <errno.h>

[edit] See also

macro which expands to POSIX-compatible thread-local error number variable
(macro variable)
displays a character string corresponding of the current error to stderr
returns a text version of a given error code
C++ documentation for Error numbers