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       error,     error_at_line,    error_message_count,    error_on_per_line,
       error_print_progname - glibc error reporting functions


       #include <error.h>

       void error(int status, int errnum, const char *format, ...);

       void error_at_line(int status, int errnum, const char *filename,
                          unsigned int linenum, const char *format, ...);

       extern unsigned int error_message_count;

       extern int error_one_per_line;

       extern void (* error_print_progname) (void);


       error() is a general error reporting function.  It flushes stdout,  and
       then  outputs  to  stderr  the  program  name, a colon and a space, the
       message specified by the printf(3)-style format string format, and,  if
       errnum  is  nonzero,  a second colon and a space followed by the string
       given by perror(errnum).  Any  arguments  required  for  format  should
       follow  format  in  the  argument  list.  The output is terminated by a
       newline character.

       The program name printed by error() is the value of the global variable
       program_invocation_name(3).   program_invocation_name initially has the
       same value as main()’s argv[0].  The value  of  this  variable  can  be
       modified to change the output of error().

       If  status has a nonzero value, then error() calls exit(3) to terminate
       the program using the given value as the exit status.

       The error_at_line() function is exactly the same as error(), except for
       the  addition  of  the  arguments  filename  and  linenum.   The output
       produced is as for error(), except that  after  the  program  name  are
       written:  a  colon,  the  value  of filename, a colon, and the value of
       linenum.  The preprocessor values __LINE__ and __FILE__ may  be  useful
       when  calling  error_at_line(), but other values can also be used.  For
       example, these arguments could refer to a location in an input file.

       If the global variable error_one_per_line is set nonzero, a sequence of
       error_at_line()  calls with the same value of filename and linenum will
       result in only one message (the first) being output.

       The global variable error_message_count counts the number  of  messages
       that have been output by error() and error_at_line().

       If  the global variable error_print_progname is assigned the address of
       a function (i.e., is not NULL), then that function is called instead of
       prefixing  the  message  with the program name and colon.  The function
       should print a suitable string to stderr.


       These functions and variables are GNU extensions,  and  should  not  be
       used in programs intended to be portable.


       err(3),   errno(3),   exit(3),  perror(3),  program_invocation_name(3),


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