std::perror (3) Linux Manual Page

std::perror – std::perror

Synopsis

Defined in header<cstdio>

    void perror(const char *s);

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

s – pointer to a null-terminated string with explanatory message

Return value

(none)

Example

// Run this code

#include <cmath>

#include <cerrno>

#include <cstdio>
int main()

{
    double not_a_number = std::log(-1.0);
    if (errno == EDOM) {
        std::perror("log(-1) failed");
    }
}

Output:

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

See also

         macro which expands to POSIX-compatible thread-local error number variable
errno (macro variable)
         returns a text version of a given error code
strerror (function)