The Fn sterror function accepts an error number argument Fa errnum and returns a pointer to the corresponding message string.
The Fn 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 Fa string is non- NULL it is pre-appended to the message string and separated from it by a colon and space (`:' ) If Fa string is NULL only the error message string is printed.
The message strings can be accessed directly using the external character array Fa sys_errlist . The external value Fa sys_nerr contains a count of the messages in Fa sys_errlist . The use of these variables is deprecated; Fn strerror should be used instead.