1FMTMSG(3)                  Linux Programmer's Manual                 FMTMSG(3)
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NAME

6       fmtmsg - print formatted error messages
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SYNOPSIS

9       #include <fmtmsg.h>
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11       int fmtmsg(long classification, const char *label,
12                  int severity, const char *text,
13                  const char *action, const char *tag);
14

DESCRIPTION

16       This  function  displays  a  message  described by its arguments on the
17       device(s) specified in the classification argument.  For messages writ‐
18       ten to stderr, the format depends on the MSGVERB environment variable.
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20       The  label  argument  identifies the source of the message.  The string
21       must consist of two colon separated parts where the first part has  not
22       more than 10 and the second part not more than 14 characters.
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24       The text argument describes the condition of the error.
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26       The action argument describes possible steps to recover from the error.
27       If it is printed, it is prefixed by "TO FIX: ".
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29       The tag argument is a reference to the online documentation where  more
30       information  can  be  found.   It  should contain the label value and a
31       unique identification number.
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33   Dummy arguments
34       Each of the arguments can have a dummy value.  The dummy classification
35       value  MM_NULLMC  (0L)  does  not  specify  any  output,  so nothing is
36       printed.  The dummy severity value NO_SEV (0) says that no severity  is
37       supplied.   The  values  MM_NULLLBL, MM_NULLTXT, MM_NULLACT, MM_NULLTAG
38       are synonyms for ((char *) 0), the empty string, and  MM_NULLSEV  is  a
39       synonym for NO_SEV.
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41   The classification argument
42       The  classification argument is the sum of values describing 4 types of
43       information.
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45       The first value defines the output channel.
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47       MM_PRINT    Output to stderr.
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49       MM_CONSOLE  Output to the system console.
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51       MM_PRINT | MM_CONSOLE
52                   Output to both.
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54       The second value is the source of the error:
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56       MM_HARD     A hardware error occurred.
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58       MM_FIRM     A firmware error occurred.
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60       MM_SOFT     A software error occurred.
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62       The third value encodes the detector of the problem:
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64       MM_APPL     It is detected by an application.
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66       MM_UTIL     It is detected by a utility.
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68       MM_OPSYS    It is detected by the operating system.
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70       The fourth value shows the severity of the incident:
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72       MM_RECOVER  It is a recoverable error.
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74       MM_NRECOV   It is a non-recoverable error.
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76   The severity argument
77       The severity argument can take one of the following values:
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79       MM_NOSEV    No severity is printed.
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81       MM_HALT     This value is printed as HALT.
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83       MM_ERROR    This value is printed as ERROR.
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85       MM_WARNING  This value is printed as WARNING.
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87       MM_INFO     This value is printed as INFO.
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89       The numeric values are between 0 and 4.  Using  addseverity(3)  or  the
90       environment  variable  SEV_LEVEL you can add more levels and strings to
91       print.
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RETURN VALUE

94       The function can return 4 values:
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96       MM_OK       Everything went smooth.
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98       MM_NOTOK    Complete failure.
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100       MM_NOMSG    Error writing to stderr.
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102       MM_NOCON    Error writing to the console.
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ENVIRONMENT

105       The environment variable MSGVERB ("message verbosity") can be  used  to
106       suppress  parts of the output to stderr.  (It does not influence output
107       to the console.)  When this variable is defined, is non-NULL, and is  a
108       colon-separated list of valid keywords, then only the parts of the mes‐
109       sage corresponding to these keywords is printed.   Valid  keywords  are
110       "label", "severity", "text", "action" and "tag".
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112       The  environment variable SEV_LEVEL can be used to introduce new sever‐
113       ity levels.  By default, only the five severity levels described  above
114       are available.  Any other numeric value would make fmtmsg() print noth‐
115       ing.  If the user puts SEV_LEVEL with a format like
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117              SEV_LEVEL=[description[:description[:...]]]
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119       in the environment of the process before the first  call  to  fmtmsg(),
120       where each description is of the form
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122              severity-keyword,level,printstring
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124       then  fmtmsg()  will also accept the indicated values for the level (in
125       addition to the standard levels 0-4), and use the indicated printstring
126       when such a level occurs.
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128       The  severity-keyword  part  is  not  used by fmtmsg() but it has to be
129       present.  The level part is a string representation of a  number.   The
130       numeric value must be a number greater than 4.  This value must be used
131       in the severity argument of fmtmsg() to select this class.  It  is  not
132       possible  to  overwrite any of the predefined classes.  The printstring
133       is the string printed when a message of  this  class  is  processed  by
134       fmtmsg().
135

VERSIONS

137       fmtmsg() is provided in glibc since version 2.1.
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CONFORMING TO

140       The  functions  fmtmsg()  and addseverity(3), and environment variables
141       MSGVERB and SEV_LEVEL come from System V.  The  function  fmtmsg()  and
142       the environment variable MSGVERB are described in POSIX.1-2001.
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NOTES

145       System  V and Unixware man pages tell us that these functions have been
146       replaced by "pfmt() and addsev()" or by "pfmt(), vpfmt(),  lfmt(),  and
147       vlfmt()", and will be removed later.
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EXAMPLE

150       #include <stdio.h>
151       #include <stdlib.h>
152       #include <fmtmsg.h>
153
154       int
155       main(void)
156       {
157           long class = MM_PRINT | MM_SOFT | MM_OPSYS | MM_RECOVER;
158           int err;
159
160           err = fmtmsg(class, "util-linux:mount", MM_ERROR,
161                       "unknown mount option", "See mount(8).",
162                       "util-linux:mount:017");
163           switch (err) {
164           case MM_OK:
165               break;
166           case MM_NOTOK:
167               printf("Nothing printed\n");
168               break;
169           case MM_NOMSG:
170               printf("Nothing printed to stderr\n");
171               break;
172           case MM_NOCON:
173               printf("No console output\n");
174               break;
175           default:
176               printf("Unknown error from fmtmsg()\n");
177           }
178           exit(EXIT_SUCCESS);
179       }
180
181       The output should be:
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183           util-linux:mount: ERROR: unknown mount option
184           TO FIX: See mount(8).  util-linux:mount:017
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186       and after
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188           MSGVERB=text:action; export MSGVERB
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190       the output becomes:
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192           unknown mount option
193           TO FIX: See mount(8).
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SEE ALSO

196       addseverity(3), perror(3)
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COLOPHON

199       This  page  is  part of release 3.22 of the Linux man-pages project.  A
200       description of the project, and information about reporting  bugs,  can
201       be found at http://www.kernel.org/doc/man-pages/.
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205                                  2008-06-14                         FMTMSG(3)
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