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 arguments on the device(s) specified in the classification argument.	For messages writ-
       ten to stderr, the format depends on the MSGVERB environment variable.

       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 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 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
       print.

RETURN VALUE

       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.

ENVIRONMENT

       The  environment variable MSGVERB ("message verbosity") can be used to suppress parts of the output to stderr.  (It does not influence out-
       put 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

	      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 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().

VERSIONS

       fmtmsg() is provided in glibc since version 2.1.

CONFORMING TO

       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.

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

       int
       main(void)
       {
	   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
");
	       break;
	   case MM_NOMSG:
	       printf("Nothing printed to stderr
");
	       break;
	   case MM_NOCON:
	       printf("No console output
");
	       break;
	   default:
	       printf("Unknown error from fmtmsg()
");
	   }
	   exit(EXIT_SUCCESS);
       }

       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)

COLOPHON

       This page is part of release 3.25 of the Linux man-pages project.  A description of the project, and information about reporting bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.

								    2008-06-14								 FMTMSG(3)