std::perror (3) - Linux Man Pages

std::perror: std::perror


std::perror - std::perror


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).


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

Return value



// 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");


  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)