void perror(const char *s);
The routine 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 function 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.
The global error list sys_errlist[? indexed by errno can be used to obtain the error message without the newline. The largest message number provided in the table is sys_nerr -1. Be careful when directly accessing this list because new error values may not have been added to sys_errlist[?.