fmtmsg(3)

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>
10
11       int fmtmsg(long classification, const char *label,
12                  int severity, const char *text,
13                  const char *action, const char *tag);
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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  [22m(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 nonrecoverable 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().
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VERSIONS

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

140   Multithreading (see pthreads(7))
141       Before glibc 2.16, the fmtmsg() function uses a static variable that is
142       not protected, so it is not thread-safe.
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144       Since glibc 2.16, the fmtmsg() function uses  a  lock  to  protect  the
145       static variable, so it is thread-safe.
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CONFORMING TO

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

153       System  V and UnixWare man pages tell us that these functions have been
154       replaced by "pfmt() and addsev()" or by "pfmt(), vpfmt(),  lfmt(),  and
155       vlfmt()", and will be removed later.
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EXAMPLE

158       #include <stdio.h>
159       #include <stdlib.h>
160       #include <fmtmsg.h>
161
162       int
163       main(void)
164       {
165           long class = MM_PRINT | MM_SOFT | MM_OPSYS | MM_RECOVER;
166           int err;
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168           err = fmtmsg(class, "util-linux:mount", MM_ERROR,
169                       "unknown mount option", "See mount(8).",
170                       "util-linux:mount:017");
171           switch (err) {
172           case MM_OK:
173               break;
174           case MM_NOTOK:
175               printf("Nothing printed\n");
176               break;
177           case MM_NOMSG:
178               printf("Nothing printed to stderr\n");
179               break;
180           case MM_NOCON:
181               printf("No console output\n");
182               break;
183           default:
184               printf("Unknown error from fmtmsg()\n");
185           }
186           exit(EXIT_SUCCESS);
187       }
188
189       The output should be:
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191           util-linux:mount: ERROR: unknown mount option
192           TO FIX: See mount(8).  util-linux:mount:017
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194       and after
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196           MSGVERB=text:action; export MSGVERB
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198       the output becomes:
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200           unknown mount option
201           TO FIX: See mount(8).
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COLOPHON

207       This  page  is  part of release 3.53 of the Linux man-pages project.  A
208       description of the project, and information about reporting  bugs,  can
209       be found at http://www.kernel.org/doc/man-pages/.
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213                                  2013-06-21                         FMTMSG(3)