NAME
	  perror, errno, sys_errlist, sys_nerr - system	error messages
SYNTAX
	  void perror (s)
	  char *s;
	  extern int errno;
	  extern char *sys_errlist[ ];
	  extern int sys_nerr;
DESCRIPTION
	  Perror produces a message on the standard error output,
	  describing the last error encountered	during a call to a
	  system or library function.  The argument string s is
	  printed first, then a	colon and a blank, then	the message
	  and a	new-line.  To be of most use, the argument string
	  should include the name of the program that incurred the
	  error.  The error number is taken from the external variable
	  errno, which is set when errors occur	but not	cleared	when
	  non-erroneous	calls are made.
	  To simplify variant formatting of messages, the array	of
	  message strings sys_errlist is provided; errno can be	used
	  as an	index in this table to get the message string without
	  the new-line.	 Sys_nerr is the largest message number
	  provided for in the table; it	should be checked because new
	  error	codes may be added to the system before	they are added
	  to the table.
SEE ALSO
	  intro(2).