perror, strerror, sys_errlist, sys_nerr - system error messages

extern int errno;
extern char *sys_errlist[];

#include <stdio.h>

void perror(string)
const char *string;

char *strerror(errnum)
int errnum;

The strerror and perror functions lookup the error message string
affiliated with an error number.

The sterror 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 and writes it, followed
by a new-line, to the stderr . If the argument string is non-NULL
it is pre-appended to the message string and separated from it by a
colon and space (’: ’). If string is NULL only the error message
string is printed.

The message strings can be accessed directly using the external
character 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.

intro(2), psignal(3)

The strerrorandperror functions are currently under development.