NAME¶

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");
}
std::printf("%f\n", not_a_number);
}

Possible output:¶

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

See also¶

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