std:: perror

Prints a textual description of the error code currently stored in the system variable errno to stderr .

The description is formed by concatenating the following components:

• the contents of the null-terminated byte string pointed to by s , followed by ": " (unless s is a null pointer or the character pointed to by s is the null character).
• implementation-defined error message string describing the error code stored in errno , followed by ' \n ' . The error message string is identical to the result of std:: strerror ( errno ) .

Parameters

Return value

(none)

Example

#include <cerrno>
#include <cmath>
#include <cstdio>
 
int main()
{
    double not_a_number = std::log(-1.0);
    if (errno == EDOM)
        std::perror("log(-1) failed");
    std::printf("%f\n", not_a_number);
}

log(-1) failed: Numerical argument out of domain
nan

See also