perror

Defined in header `<stdio.h>`
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 strerror(errno).

Parameters

s

-

pointer to a null-terminated string with explanatory message

Return value

(none)

Example

Run this code

#include <stdio.h>
 
int main(void)
{
    FILE *f = fopen("non_existent", "r");
    if (f == NULL) {
        perror("fopen() failed");
    } else {
        fclose(f);
    }
}

Output:

fopen() failed: No such file or directory

References

C11 standard (ISO/IEC 9899:2011):

7.21.10.4 The perror function (p: 339)

C99 standard (ISO/IEC 9899:1999):

7.19.10.4 The perror function (p: 305)

C89/C90 standard (ISO/IEC 9899:1990):

4.9.10.4 The perror function

Language
Headers
Type support
Program utilities
Variadic function support
Error handling
Dynamic memory management
Date and time utilities
Strings library
Algorithms
Numerics
Input/output support
Localization support
Atomic operations (C11)
Thread support (C11)
Technical Specifications

perror

Parameters

Return value

Example

References

See also