fmtmsg(3C)fmtmsg(3C)NAMEfmtmsg - display a message on stderr or system console
SYNOPSIS
#include <fmtmsg.h>
int fmtmsg(long classification, const char *label, int severity,
const char *text, const char *action, const char *tag);
DESCRIPTION
Based on a message's classification component, fmtmsg writes a formatted
message to stderr, to the console, or to both.
fmtmsg can be used instead of the traditional printf interface to display
messages to stderr. fmtmsg, in conjunction with gettxt, provides a
simple interface for producing language-independent applications.
A formatted message consists of up to five standard components as defined
below. The component, classification, is not part of the standard
message displayed to the user, but rather defines the source of the
message and directs the display of the formatted message.
classification
Contains identifiers from the following groups of major
classifications and subclassifications. Any one identifier from a
subclass may be used in combination by ORing the values together
with a single identifier from a different subclass. Two or more
identifiers from the same subclass should not be used together,
with the exception of identifiers from the display subclass. (Both
display subclass identifiers may be used so that messages can be
displayed to both stderr and the system console).
``Major classifications'' identify the source of the condition.
Identifiers are: MM_HARD (hardware), MM_SOFT (software), and
MM_FIRM (firmware).
``Message source subclassifications'' identify the type of
software in which the problem is spotted. Identifiers are:
MM_APPL (application), MM_UTIL (utility), and MM_OPSYS
(operating system).
``Display subclassifications'' indicate where the message is to
be displayed. Identifiers are: MM_PRINT to display the message
on the standard error stream, MM_CONSOLE to display the message
on the system console. Neither, either, or both identifiers may
be used.
``Status subclassifications'' indicate whether the application
will recover from the condition. Identifiers are: MM_RECOVER
(recoverable) and MM_NRECOV (non-recoverable).
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An additional identifier, MM_NULLMC, indicates that no
classification component is supplied for the message.
label Identifies the source of the message. The format of this component
is two fields separated by a colon. The first field is up to 10
characters long; the second is up to 14 characters. Suggested
usage is that label identifies the package in which the application
resides as well as the program or application name. For example,
the label UX:cat indicates the UNIX System V package and the cat
application.
severity
Indicates the seriousness of the condition. Identifiers for the
standard levels of severity are:
MM_HALT indicates that the application has encountered a severe
fault and is halting. Produces the print string HALT.
MM_ERROR indicates that the application has detected a fault.
Produces the print string ERROR.
MM_WARNING indicates a condition out of the ordinary that might
be a problem and should be watched. Produces the print string
WARNING.
MM_INFO provides information about a condition that is not in
error. Produces the print string INFO.
MM_NOSEV indicates that no severity level is supplied for the
message.
Other severity levels may be added by using the addseverity
routine.
text Describes the condition that produced the message. The text string
is not limited to a specific size.
action
Describes the first step to be taken in the error recovery process.
fmtmsg precedes each action string with the prefix: TO FIX:. The
action string is not limited to a specific size.
tag An identifier which references on-line documentation for the
message. Suggested usage is that tag includes the label and a
unique identifying number. A sample tag is UX:cat:146.
Environment Variables
There are two environment variables that control the behavior of fmtmsg:
MSGVERB and SEV_LEVEL.
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MSGVERB tells fmtmsg which message components it is to select when
writing messages to stderr. The value of MSGVERB is a colon-separated
list of optional keywords. MSGVERB can be set as follows:
MSGVERB=[keyword[:keyword[:...]]]
export MSGVERB
Valid keywords are: label, severity, text, action, and tag. If MSGVERB
contains a keyword for a component and the component's value is not the
component's null value, fmtmsg includes that component in the message
when writing the message to stderr. If MSGVERB does not include a
keyword for a message component, that component is not included in the
display of the message. The keywords may appear in any order. If
MSGVERB is not defined, if its value is the null-string, if its value is
not of the correct format, or if it contains keywords other than the
valid ones listed above, fmtmsg selects all components.
The first time fmtmsg is called, it examines the MSGVERB environment
variable to see which message components it is to select when generating
a message to write to the standard error stream, stderr. The values
accepted on the initial call are saved for future calls.
MSGVERB affects only which components are selected for display to the
standard error stream. All message components are included in console
messages.
SEV_LEVEL defines severity levels and associates print strings with them
for use by fmtmsg. The standard severity levels shown below cannot be
modified. Additional severity levels can also be defined, redefined, and
removed using addseverity [see addseverity(3C)]. If the same severity
level is defined by both SEV_LEVEL and addseverity, the definition by
addseverity is controlling.
0 (no severity is used)
1 HALT
2 ERROR
3 WARNING
4 INFO
SEV_LEVEL can be set as follows:
SEV_LEVEL=[description[:description[:...]]]
export SEV_LEVEL
description is a comma-separated list containing three fields:
description=severity_keyword,level,printstring
severity_keyword is a character string that is used as the keyword on the
-s severity option to the fmtmsg command. (This field is not used by the
fmtmsg function.)
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level is a character string that evaluates to a positive integer (other
than 0, 1, 2, 3, or 4, which are reserved for the standard severity
levels). If the keyword severity_keyword is used, level is the severity
value passed on to the fmtmsg function.
printstring is the character string used by fmtmsg in the standard
message format whenever the severity value level is used.
If a description in the colon list is not a three-field comma list, or,
if the second field of a comma list does not evaluate to a positive
integer, that description in the colon list is ignored.
The first time fmtmsg is called, it examines the SEV_LEVEL environment
variable, if defined, to see whether the environment expands the levels
of severity beyond the five standard levels and those defined using
addseverity. The values accepted on the initial call are saved for
future calls.
Use in Applications
One or more message components may be systematically omitted from
messages generated by an application by using the null value of the
argument for that component.
The table below indicates the null values and identifiers for fmtmsg
arguments.
______________________________________________
Argument Type Null-Value Identifier
______________________________________________
label char* (char*) NULL MM_NULLLBL
severity int 0 MM_NULLSEV
class long 0L MM_NULLMC
text char* (char*) NULL MM_NULLTXT
action char* (char*) NULL MM_NULLACT
tag char* (char*) NULL MM_NULLTAG
______________________________________________
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Another means of systematically omitting a component is by omitting the
component keyword(s) when defining the MSGVERB environment variable (see
the ``Environment Variables'' section).
EXAMPLES
Example 1:
The following example of fmtmsg:
fmtmsg(MM_PRINT, "UX:cat", MM_ERROR, "invalid syntax", "refer to
manual", "UX:cat:001")
produces a complete message in the standard message format:
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UX:cat: ERROR: invalid syntax
TO FIX: refer to manual UX:cat:001
Example 2:
When the environment variable MSGVERB is set as follows:
MSGVERB=severity:text:action
and the Example 1 is used, fmtmsg produces:
ERROR: invalid syntax
TO FIX: refer to manual
Example 3:
When the environment variable SEV_LEVEL is set as follows:
SEV_LEVEL=note,5,NOTE
the following call to fmtmsg:
fmtmsg(MM_UTIL | MM_PRINT, "UX:cat", 5, "invalid syntax", "refer to
manual", "UX:cat:001")
produces:
UX:cat: NOTE: invalid syntax
TO FIX: refer to manual UX:cat:001
NOTES
A slightly different standard error message format and a new developer
interface, pfmt, is being introduced as the replacement for fmtmsg. A
similar interface, lfmt, is also being introduced for producing a
standard format message and forwarding messages to the console and/or to
the system message logging and monitoring facilities. fmtmsg will be
removed at a future time.
SEE ALSOfmtmsg(1), addseverity(3C), gettxt(3C), printf(3S).
DIAGNOSTICS
The exit codes for fmtmsg are the following:
MM_OK The function succeeded.
MM_NOTOK The function failed completely.
MM_NOMSG The function was unable to generate a message on the standard
error stream, but otherwise succeeded.
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MM_NOCON The function was unable to generate a console message, but
otherwise succeeded.
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