STRERROR(3)

NAME
perror, strerror, sys_errlist, sys_nerr - system error messages

SYNOPSIS
#include <stdio.h>
void
perror(const char *string);
extern const char * const sys_errlist[];
extern const int sys_nerr;
#include <string.h>
char *
strerror(int errnum);

DESCRIPTION
The strerror() and perror() functions look up the error message string corresponding to an error number.

The strerror() function accepts an error number argument errnum and returns a pointer to the corresponding message string.

The perror() function finds the error message corresponding to the current value of the global variable errno (intro(2)) and writes it, followed by a newline, to the standard error file descriptor. If the argument string is non-NULL, it is prepended to the message string and separated from it by a colon and space (‘: ’). If string is NULL, only the error message string is printed.

If errnum is not a recognized error number, the error message string will contain “Unknown error: ” followed by the error number in decimal.

The message strings can be accessed directly using the external array sys_errlist. The external value sys_nerr contains a count of the messages in sys_errlist. The use of these variables is deprecated; strerror() should be used instead.

SEE ALSO
intro(2), psignal(3)

HISTORY
The strerror() and perror() functions first appeared in 4.4BSD.

BUGS
For unknown error numbers, the strerror() function will return its result in a static buffer which may be overwritten by subsequent calls.

Programs that use the deprecated sys_errlist variable often fail to compile because they declare it inconsistently.