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       fmtmsg - print formatted error messages


       #include <fmtmsg.h>

       int fmtmsg(long classification, const char *label,
                  int severity, const char *text,
                  const char *action, const char *tag);


       This  function  displays  a  message  described by its arguments on the
       device(s) specified  in  the  classification  argument.   For  messages
       written  to  stderr,  the  format  depends  on  the MSGVERB environment

       The label argument identifies the source of the  message.   The  string
       must  consist of two colon separated parts where the first part has not
       more than 10 and the second part not more than 14 characters.

       The text argument describes the condition of the error.

       The action argument describes possible steps to recover from the error.
       If it is printed, it is prefixed by "TO FIX: ".

       The  tag argument is a reference to the online documentation where more
       information can be found.  It should contain  the  label  value  and  a
       unique identification number.

   Dummy arguments
       Each of the arguments can have a dummy value.  The dummy classification
       value MM_NULLMC (0L)  does  not  specify  any  output,  so  nothing  is
       printed.   The dummy severity value NO_SEV (0) says that no severity is
       supplied.  The values MM_NULLLBL,  MM_NULLTXT,  MM_NULLACT,  MM_NULLTAG
       are  synonyms  for  ((char *) 0), the empty string, and MM_NULLSEV is a
       synonym for NO_SEV.

   The classification argument
       The classification argument is the sum of values describing 4 types  of

       The first value defines the output channel.

       MM_PRINT    Output to stderr.

       MM_CONSOLE  Output to the system console.

                   Output to both.

       The second value is the source of the error:

       MM_HARD     A hardware error occurred.

       MM_FIRM     A firmware error occurred.

       MM_SOFT     A software error occurred.

       The third value encodes the detector of the problem:

       MM_APPL     It is detected by an application.

       MM_UTIL     It is detected by a utility.

       MM_OPSYS    It is detected by the operating system.

       The fourth value shows the severity of the incident:

       MM_RECOVER  It is a recoverable error.

       MM_NRECOV   It is a nonrecoverable error.

   The severity argument
       The severity argument can take one of the following values:

       MM_NOSEV    No severity is printed.

       MM_HALT     This value is printed as HALT.

       MM_ERROR    This value is printed as ERROR.

       MM_WARNING  This value is printed as WARNING.

       MM_INFO     This value is printed as INFO.

       The  numeric  values  are between 0 and 4.  Using addseverity(3) or the
       environment variable SEV_LEVEL you can add more levels and  strings  to


       The function can return 4 values:

       MM_OK       Everything went smooth.

       MM_NOTOK    Complete failure.

       MM_NOMSG    Error writing to stderr.

       MM_NOCON    Error writing to the console.


       The  environment  variable MSGVERB ("message verbosity") can be used to
       suppress parts of the output to stderr.  (It does not influence  output
       to  the console.)  When this variable is defined, is non-NULL, and is a
       colon-separated list of valid keywords, then  only  the  parts  of  the
       message corresponding to these keywords is printed.  Valid keywords are
       "label", "severity", "text", "action" and "tag".

       The environment  variable  SEV_LEVEL  can  be  used  to  introduce  new
       severity  levels.   By default, only the five severity levels described
       above are available.  Any other numeric value would make fmtmsg() print
       nothing.  If the user puts SEV_LEVEL with a format like


       in  the  environment  of the process before the first call to fmtmsg(),
       where each description is of the form


       then fmtmsg() will also accept the indicated values for the  level  (in
       addition to the standard levels 0-4), and use the indicated printstring
       when such a level occurs.

       The severity-keyword part is not used by fmtmsg()  but  it  has  to  be
       present.   The  level part is a string representation of a number.  The
       numeric value must be a number greater than 4.  This value must be used
       in  the  severity argument of fmtmsg() to select this class.  It is not
       possible to overwrite any of the predefined classes.   The  printstring
       is  the  string  printed  when  a message of this class is processed by


       fmtmsg() is provided in glibc since version 2.1.


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


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


       #include <stdio.h>
       #include <stdlib.h>
       #include <fmtmsg.h>

           long class = MM_PRINT | MM_SOFT | MM_OPSYS | MM_RECOVER;
           int err;

           err = fmtmsg(class, "util-linux:mount", MM_ERROR,
                       "unknown mount option", "See mount(8).",
           switch (err) {
           case MM_OK:
           case MM_NOTOK:
               printf("Nothing printed\n");
           case MM_NOMSG:
               printf("Nothing printed to stderr\n");
           case MM_NOCON:
               printf("No console output\n");
               printf("Unknown error from fmtmsg()\n");

       The output should be:

           util-linux:mount: ERROR: unknown mount option
           TO FIX: See mount(8).  util-linux:mount:017

       and after

           MSGVERB=text:action; export MSGVERB

       the output becomes:

           unknown mount option
           TO FIX: See mount(8).


       addseverity(3), perror(3)


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