NAME

perror, errno, sys_errlist, sys_nerr − system error messages

SYNOPSIS

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). 

Version 2.1  —  January 02, 1985