fmtmsg

fmtmsg(3)                  Linux Programmer's Manual                 fmtmsg(3)



NAME
       fmtmsg - print formatted error messages

SYNOPSIS
       #include <fmtmsg.h>

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


DESCRIPTION
       This  function  displays  a  message described by its parameters on the
       device(s) specified in the classification parameter. For messages writ-
       ten  to stderr, the format depends on the MSGVERB environment variable.

       The label parameter 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 parameter describes the condition of the error.

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

       The tag parameter 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 parameters
       Each of the parameters 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 parameter
       The classification parameter is the sum of values describing 4 types of
       information.

       The first value defines the output channel.

       MM_PRINT    Output to stderr.

       MM_CONSOLE  Output to the system console.

       MM_PRINT | MM_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 non-recoverable error.

   The severity parameter
       The severity parameter 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() or the
       environment variable SEV_LEVEL you can add more levels and  strings  to
       print.

ENVIRONMENT
       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 mes-
       sage  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  sever-
       ity  levels.  By default, only the five severity levels described above
       are available.  Any other numeric value would make fmtmsg() print noth-
       ing.  If the user puts SEV_LEVEL with a format like

              SEV_LEVEL=[description[:description[:...]]]

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

              severity-keyword,level,printstring

       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 parameter 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().

RETURN VALUES
       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.

CONFORMING TO
       The functions fmtmsg() and  addseverity(),  and  environment  variables
       MSGVERB  and  SEV_LEVEL  come  from System V (XPG4-UNIX).  The function
       fmtmsg() and the environment variable MSGVERB are  described  in  POSIX
       1003.1-2001.

NOTES
       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.

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

       int main() {
         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).", "util-linux:mount:017");
         switch(err) {
           case MM_OK:
             break;
           case MM_NOTOK:
             printf("Nothing printed\n");
             break;
           case MM_NOMSG:
             printf("Nothing printed to stderr\n");
             break;
           case MM_NOCON:
             printf("No console output\n");
             break;
           default:
             printf("Unknown error from fmtmsg()\n");
         }
         return 0;
       }

       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).

SEE ALSO
       addseverity(3), perror(3)



                                  2003-11-01                         fmtmsg(3)