1fmtmsg(3) Linux Programmer's Manual fmtmsg(3)
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6 fmtmsg - print formatted error messages
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9 #include <fmtmsg.h>
10 int fmtmsg(long classification, const char *label,
12 int severity, const char *text,
13 const char *action, const char *tag);
14
17 This function displays a message described by its parameters on the
18 device(s) specified in the classification parameter. For messages writ‐
19 ten to stderr, the format depends on the MSGVERB environment variable.
20 The label parameter identifies the source of the message. The string
22 must consist of two colon separated parts where the first part has not
23 more than 10 and the second part not more than 14 characters.
24 The text parameter describes the condition of the error.
26 The action parameter describes possible steps to recover from the
28 error. If it is printed, it is prefixed by "TO FIX: ".
29 The tag parameter is a reference to the online documentation where more
31 information can be found. It should contain the label value and a
32 unique identification number.
33 Dummy parameters
35 Each of the parameters can have a dummy value. The dummy classification
36 value MM_NULLMC [22m(0L) does not specify any output, so nothing is
37 printed. The dummy severity value NO_SEV (0) says that no severity is
38 supplied. The values MM_NULLLBL, MM_NULLTXT, MM_NULLACT, MM_NULLTAG
39 are synonyms for ((char *) 0), the empty string, and MM_NULLSEV is a
40 synonym for NO_SEV.
41 The classification parameter
43 The classification parameter is the sum of values describing 4 types of
44 information.
45 The first value defines the output channel.
47 MM_PRINT Output to stderr.
49 MM_CONSOLE Output to the system console.
51 MM_PRINT | MM_CONSOLE
53 Output to both.
54 The second value is the source of the error:
56 MM_HARD A hardware error occurred.
58 MM_FIRM A firmware error occurred.
60 MM_SOFT A software error occurred.
62 The third value encodes the detector of the problem:
64 MM_APPL It is detected by an application.
66 MM_UTIL It is detected by a utility.
68 MM_OPSYS It is detected by the operating system.
70 The fourth value shows the severity of the incident:
72 MM_RECOVER It is a recoverable error.
74 MM_NRECOV It is a non-recoverable error.
76 The severity parameter
78 The severity parameter can take one of the following values:
79 MM_NOSEV No severity is printed.
81 MM_HALT This value is printed as HALT.
83 MM_ERROR This value is printed as ERROR.
85 MM_WARNING This value is printed as WARNING.
87 MM_INFO This value is printed as INFO.
89 The numeric values are between 0 and 4. Using addseverity() or the
91 environment variable SEV_LEVEL you can add more levels and strings to
92 print.
93
95 The environment variable MSGVERB ("message verbosity") can be used to
96 suppress parts of the output to stderr. (It does not influence output
97 to the console.) When this variable is defined, is non-NULL, and is a
98 colon-separated list of valid keywords, then only the parts of the mes‐
99 sage corresponding to these keywords is printed. Valid keywords are
100 "label", "severity", "text", "action" and "tag".
101 The environment variable SEV_LEVEL can be used to introduce new sever‐
103 ity levels. By default, only the five severity levels described above
104 are available. Any other numeric value would make fmtmsg() print noth‐
105 ing. If the user puts SEV_LEVEL with a format like
106 SEV_LEVEL=[description[:description[:...]]]
108 in the environment of the process before the first call to fmtmsg(),
110 where each description is of the form
111 severity-keyword,level,printstring
113 then fmtmsg() will also accept the indicated values for the level (in
115 addition to the standard levels 0-4), and use the indicated printstring
116 when such a level occurs.
117 The severity-keyword part is not used by fmtmsg() but it has to be
119 present. The level part is a string representation of a number. The
120 numeric value must be a number greater than 4. This value must be used
121 in the severity parameter of fmtmsg() to select this class. It is not
122 possible to overwrite any of the predefined classes. The printstring
123 is the string printed when a message of this class is processed by
124 fmtmsg().
125
127 The function can return 4 values:
128 MM_OK Everything went smooth.
130 MM_NOTOK Complete failure.
132 MM_NOMSG Error writing to stderr.
134 MM_NOCON Error writing to the console.
136
138 The functions fmtmsg() and addseverity(), and environment variables
139 MSGVERB and SEV_LEVEL come from System V. The function fmtmsg() and
140 the environment variable MSGVERB are described in POSIX.1-2001.
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143 System V and Unixware man pages tell us that these functions have been
144 replaced by "pfmt() and addsev()" or by "pfmt(), vpfmt(), lfmt(), and
145 vlfmt()", and will be removed later.
146
148 #include <stdio.h>
149 #include <fmtmsg.h>
150 int main() {
152 long class = MM_PRINT | MM_SOFT | MM_OPSYS | MM_RECOVER;
153 int err;
154 err = fmtmsg(class, "util-linux:mount", MM_ERROR,
155 "unknown mount option", "See mount(8).", "util-linux:mount:017");
156 switch(err) {
157 case MM_OK:
158 break;
159 case MM_NOTOK:
160 printf("Nothing printed\n");
161 break;
162 case MM_NOMSG:
163 printf("Nothing printed to stderr\n");
164 break;
165 case MM_NOCON:
166 printf("No console output\n");
167 break;
168 default:
169 printf("Unknown error from fmtmsg()\n");
170 }
171 return 0;
172 }
173 The output should be:
175 util-linux:mount: ERROR: unknown mount option
176 TO FIX: See mount(8). util-linux:mount:017
177 and after
178 MSGVERB=text:action; export MSGVERB
179 the output becomes:
180 unknown mount option
181 TO FIX: See mount(8).
182
184 addseverity(3), perror(3)
185 2003-11-01 fmtmsg(3)