PERROR(III)                  11/5/73                  PERROR(III)

     perror, sys_errlist, sys_nerr, errno - system error messages

     char *s;

     int sys_nerr;
     char *sys_errlist[];

     int errno;

     Perror produces a short error message  describing  the  last
     error  encountered during a call to the system from a C pro-
     gram.  First the argument string s is printed, then a colon,
     then  the  message and a new-line.  Most usefully, the argu-
     ment string is the name of the program  which  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 vector of
     message strings sys_errlist is provided; errno can  be  used
     as  an index in this table to get the message string without
     the newline.  Sys_nerr is the largest message number provid-
     ed  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.

     Introduction to System Calls


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