error, error_at_line, error_message_count, error_one_per_line, error_print_progname - glibc error reporting functions
Standard C library (libc, -lc)
#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 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
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; otherwise it returns after printing the error
message.
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.
For an explanation of the terms used in this section, see attributes(7).
| Interface | Attribute | Value |
error() |
Thread safety | MT-Safe locale |
| Thread safety | MT-Unsafe race: error_at_line/error_one_per_line locale |
The internal error_one_per_line variable is accessed
(without any form of synchronization, but since it's an int
used once, it should be safe enough) and, if error_one_per_line
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 cancelation, so it can be interrupted only after one of
the two variables is modified. After that,
error_at_line() is very much like
error().
GNU.