Name
error, error_at_line, error_message_count, error_one_per_line, error_print_progname - glibc error reporting functionsLibrary
Standard C library ( libc ", " -lc )Synopsis
#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);
Description
error() is a general error-reporting function. It flushesstdout
, 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
.
Attributes
For an explanation of the terms used in this section, see attributes(7).Interface | Attribute | Value |
T} | Thread safety | MT-Safe locale |
T} | 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()