1ERROR(3) Linux Programmer's Manual ERROR(3)
2
6 error, error_at_line, error_message_count, error_one_per_line,
7 error_print_progname - glibc error reporting functions
8
10 #include <error.h>
11 void error(int status, int errnum, const char *format, ...);
13 void error_at_line(int status, int errnum, const char *filename,
15 unsigned int linenum, const char *format, ...);
16 extern unsigned int error_message_count;
18 extern int error_one_per_line;
20 extern void (*error_print_progname) (void);
22
24 error() is a general error-reporting function. It flushes stdout, and
25 then outputs to stderr the program name, a colon and a space, the mes‐
26 sage specified by the printf(3)-style format string format, and, if
27 errnum is nonzero, a second colon and a space followed by the string
28 given by strerror(errnum). Any arguments required for format should
29 follow format in the argument list. The output is terminated by a new‐
30 line character.
31 The program name printed by error() is the value of the global variable
33 program_invocation_name(3). program_invocation_name initially has the
34 same value as main()'s argv[0]. The value of this variable can be mod‐
35 ified to change the output of error().
36 If status has a nonzero value, then error() calls exit(3) to terminate
38 the program using the given value as the exit status.
39 The error_at_line() function is exactly the same as error(), except for
41 the addition of the arguments filename and linenum. The output pro‐
42 duced is as for error(), except that after the program name are writ‐
43 ten: a colon, the value of filename, a colon, and the value of linenum.
44 The preprocessor values __LINE__ and __FILE__ may be useful when call‐
45 ing error_at_line(), but other values can also be used. For example,
46 these arguments could refer to a location in an input file.
47 If the global variable error_one_per_line is set nonzero, a sequence of
49 error_at_line() calls with the same value of filename and linenum will
50 result in only one message (the first) being output.
51 The global variable error_message_count counts the number of messages
53 that have been output by error() and error_at_line().
54 If the global variable error_print_progname is assigned the address of
56 a function (i.e., is not NULL), then that function is called instead of
57 prefixing the message with the program name and colon. The function
58 should print a suitable string to stderr.
59
61 For an explanation of the terms used in this section, see
62 attributes(7).
63 ┌────────────────┬───────────────┬───────────────────────────────────┐
65 │Interface │ Attribute │ Value │
66 ├────────────────┼───────────────┼───────────────────────────────────┤
67 │error() │ Thread safety │ MT-Safe locale │
68 ├────────────────┼───────────────┼───────────────────────────────────┤
69 │error_at_line() │ Thread safety │ MT-Unsafe race: │
70 │ │ │ error_at_line/error_one_per_line │
71 │ │ │ locale │
72 └────────────────┴───────────────┴───────────────────────────────────┘
73 The internal error_one_per_line variable is accessed (without any form
74 of synchronization, but since it's an int used once, it should be safe
75 enough) and, if error_one_per_line is set nonzero, the internal static
76 variables (not exposed to users) used to hold the last printed filename
77 and line number are accessed and modified without synchronization; the
78 update is not atomic and it occurs before disabling cancellation, so it
79 can be interrupted only after one of the two variables is modified.
80 After that, error_at_line() is very much like error().
81
83 These functions and variables are GNU extensions, and should not be
84 used in programs intended to be portable.
85
87 err(3), errno(3), exit(3), perror(3), program_invocation_name(3), str‐
88 error(3)
89
91 This page is part of release 4.15 of the Linux man-pages project. A
92 description of the project, information about reporting bugs, and the
93 latest version of this page, can be found at
94 https://www.kernel.org/doc/man-pages/.
95GNU 2017-09-15 ERROR(3)