error, error_at_line, error_message_count, error_one_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
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
strerror(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
argv. The value of this variable can be
modified to change the output of error().
The error_at_line() function is exactly the same as
error(), except for the addition of the arguments
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
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
linenum will result in only one
message (the first) being output.
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
For an explanation of the terms used in this section, see attributes(7).
|error()||Thread safety||MT-Safe locale|
|error_at_line()||Thread safety||MT-Unsafe race: error_at_line/error_one_per_line locale|
error_one_per_line variable is accessed
(without any form of synchronization, but since it's an
used once, it should be safe enough) and, if
is set nonzero, the internal static variables (not exposed to users)
used to hold the last printed filename and line number are accessed and
modified without synchronization; the update is not atomic and it occurs
before disabling cancellation, so it can be interrupted only after one
of the two variables is modified. After that,
error_at_line() is very much like
These functions and variables are GNU extensions, and should not be used in programs intended to be portable.
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