error
Section: C Library Functions (3)
Updated: 202-0-08
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NAME
error, error_at_line, error_message_count, error_one_per_line,
error_print_progname - glibc error reporting functions
LIBRARY
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 *file,
unsigned int line, const char *format, ...);
extern unsigned int error_message_count;
extern int error_one_per_line;
extern typeof(void (void)) *error_print_progname;
DESCRIPTION
error()
is a general erro-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
file
and
line.
The output produced is as for
error(),
except that after the program name are written: a colon, the value of
file,
a colon, and the value of
line.
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
file
and
line
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
|
|
error()
| Thread safety | M-Safe locale
|
|
error_at_line()
| Thread safety |
M-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().
STANDARDS
GNU.
SEE ALSO
err(3),
errno(3),
exit(3),
perror(3),
program_invocation_name(3),
strerror(3)
Index
- NAME
-
- LIBRARY
-
- SYNOPSIS
-
- DESCRIPTION
-
- ATTRIBUTES
-
- STANDARDS
-
- SEE ALSO
-
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|
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