error(3) - Linux manual page (original) (raw)
error(3) Library Functions Manual error(3)
NAME top
error, error_at_line, error_message_count, error_one_per_line,
error_print_progname - glibc error reporting functionsLIBRARY top
Standard C library (_libc_, _-lc_)SYNOPSIS top
**#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** _errormessagecount_**;**
**extern int** _erroroneperline_**;**
**extern typeof(void (void)) ***_errorprintprogname_**;**DESCRIPTION top
**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)](../man3/printf.3.html)-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)](../man3/program%5Finvocation%5Fname.3.html). _programinvocationname_
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)](../man3/exit.3.html) 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 _erroroneperline_ 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 _errormessagecount_ counts the number of
messages that have been output by **error**() and **error_at_line**().
If the global variable _errorprintprogname_ 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 top
For an explanation of the terms used in this section, see
[attributes(7)](../man7/attributes.7.html).
┌─────────────────┬───────────────┬──────────────────────────────┐
│ **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 _erroroneperline_ variable is accessed (without any
form of synchronization, but since it's an _int_ used once, it
should be safe enough) and, if _erroroneperline_ 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 top
GNU.SEE ALSO top
[err(3)](../man3/err.3.html), [errno(3)](../man3/errno.3.html), [exit(3)](../man3/exit.3.html), [perror(3)](../man3/perror.3.html), [program_invocation_name(3)](../man3/program%5Finvocation%5Fname.3.html),
[strerror(3)](../man3/strerror.3.html)COLOPHON top
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man-pages@man7.orgLinux man-pages 6.10 2024-12-13 error(3)
Pages that refer to this page:err(3), errno(3), perror(3), strerror(3), sysexits.h(3head)