fmtmsg(3C) (Essential Utilities) fmtmsg(3C)
NAME
fmtmsg - 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-
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recoverable).
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.
Additional 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.
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fmtmsg(3C) (Essential Utilities) fmtmsg(3C)
Environment Variables
There are two environment variables that control the behavior of
fmtmsg: MSGVERB and SEV_LEVEL.
MSGVERB tells fmtmsg which message components it is to select when
writing messages to stderr. The value of MSGVERB is a colon-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
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fmtmsg(3C) (Essential Utilities) fmtmsg(3C)
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.)
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|
|_____________________________________________|
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).
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fmtmsg(3C) (Essential Utilities) fmtmsg(3C)
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.
MM_NOCON The function was unable to generate a console message,
but otherwise succeeded.
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:
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
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fmtmsg(3C) (Essential Utilities) fmtmsg(3C)
SEE ALSO
addseverity(3C), gettxt(3C), printf(3S).
fmtmsg(1) in the User's Reference Manual.
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