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NAME | SYNOPSIS | DESCRIPTION | ATTRIBUTES | CONFORMING TO | SEE ALSO | COLOPHON |
ERROR(3) Linux Programmer's Manual ERROR(3)
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 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.
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 │
├────────────────┼───────────────┼───────────────────────────────────┤
│error_at_line() │ 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 cancellation, so it can be interrupted only after
one of the two variables is modified. After that, error_at_line() is
very much like error().
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),
strerror(3)
This page is part of release 4.12 of the Linux man-pages project. A
description of the project, information about reporting bugs, and the
latest version of this page, can be found at
https://www.kernel.org/doc/man-pages/.
GNU 2016-10-08 ERROR(3)
Pages that refer to this page: err(3), errno(3), perror(3), strerror(3)