perror (3) Linux Manual Page

perror – print a system error message

Synopsis

#include <stdio.h>
void perror(const char *s);
#include <errno.h>

const char * const sys_errlist[];
int sys_nerr;
int errno; /* Not really declared this way; see errno(3) */ Feature Test Macro Requirements for glibc (see feature_test_macros(7)): sys_errlist, sys_nerr:
    From glibc 2.19 to 2.31:
        _DEFAULT_SOURCE
    Glibc 2.19 and earlier:
        _BSD_SOURCE

Description

The perror() function produces a message on standard error describing the last error encountered during a call to a system or library function.

First (if s is not NULL and *s is not a null byte (‘