C Programming/stdio.h/perror
< C Programming | stdio.h
The POSIX error function, perror, is used in C and C++ to print an error message to stderr, based on the error state stored in errno.[1]It prints str and an implementation-defined error message corresponding to the global variable errno.
History edit
The definition of perror was first released in Issue 1 of the System V Interface Definition.
Usage edit
Inclusion edit
#include <stdio.h>
Declaration edit
void perror(const char* prefix);
Example edit
int fd = open("/etc/passwd", O_RDONLY);
if (fd == -1) {
perror("open");
exit(1);
}
Semantics edit
If the parameter prefix is non-NULL, perror will first print prefix followed by a colon and a space to standard error. Then, it will print the result of strerror to standard error, followed by a newline character. For instance the above example may print
open: Permission denied
References edit
- ↑ ISO/IEC 9899:1999 specification (PDF). p. 305, § 7.19.10.2.