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
parameters on the device(s) specified in the classification parameter. For
messages written 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.
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 is the sum of values describing 4 types of information.
The first value defines the output channel.
MM_PRINTOutput to stderr.
MM_CONSOLEOutput to the system console.
Output to both.
The second value is the source of the error:
MM_HARDA hardware error occurred.
MM_FIRMA firmware error occurred.
MM_SOFTA software error occurred.
The third value encodes the detector of the problem:
MM_APPLIt is detected by an application.
MM_UTILIt is detected by a utility.
MM_OPSYSIt is detected by the operating system.
The fourth value shows the severity of the incident:
MM_RECOVERIt is a recoverable error.
MM_NRECOVIt is a non-recoverable error.
The severity
parameter can take one of the following values:
MM_NOSEVNo severity is printed.
MM_HALTThis value is printed as HALT.
MM_ERRORThis value is printed as ERROR.
MM_WARNINGThis value is printed as WARNING.
MM_INFOThis 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.
The function can return 4 values:
MM_OKEverything went smooth.
MM_NOTOKComplete failure.
MM_NOMSGError writing to stderr.
MM_NOCONError 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
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().
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>
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\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");
}
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).
This page is part of release 2.77 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/.
|
Copyright 2002 walter harms (walter.harmsinformatik.uni-oldenburg.de) Distributed under GPL adapted glibc info page This should run as 'Guru Meditation' (amiga joke :) The function is quite complex and deserves an example Polished, aeb, 2003-11-01 |