C Perror Example

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

#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

See also

strerrorstrerror_sstrerrorlen_s (C11)(C11)

returns a text version of a given error code (function)