The fmtmsg() function shall display messages in a specified
format instead of the traditional printf() function.
Based on a message's classification component, fmtmsg() shall
write a formatted message either to standard error, to the
console, or to both.
A formatted message consists of up to five components as defined below.
The component classification is not part of a
message displayed to the user, but defines the source of the message
and directs the display of the formatted message.
Contains the sum of identifying values constructed from the constants
defined below. Any one identifier from a subclass may be
used in combination 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 standard error and the system
Identifies the source of the condition. Identifiers are: MM_HARD (hardware),
MM_SOFT (software), and MM_FIRM (firmware).
Message Source Subclassifications
Identifies the type of software in which the problem is detected.
Identifiers are: MM_APPL (application), MM_UTIL (utility), and
MM_OPSYS (operating system).
Indicates 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. One or both
identifiers may be used.
Indicates whether the application can recover from the condition.
Identifiers are: MM_RECOVER (recoverable) and MM_NRECOV
An additional identifier, MM_NULLMC, indicates that no classification
component is supplied for the message.
Identifies the source of the message. The format is two fields separated
by a colon. The first field is up to 10 bytes, the
second is up to 14 bytes.
Indicates the seriousness of the condition. Identifiers for the levels
of severity are:
Indicates that the application has encountered a severe fault and
is halting. Produces the string "HALT" .
Indicates that the application has detected a fault. Produces the
string "ERROR" .
Indicates a condition that is out of the ordinary, that might be a
problem, and should be watched. Produces the string
Provides information about a condition that is not in error. Produces
the string "INFO" .
Indicates that no severity level is supplied for the message.
Describes the error condition that produced the message. The character
string is not limited to a specific size. If the
character string is empty, then the text produced is unspecified.
Describes the first step to be taken in the error-recovery process.
The fmtmsg() function precedes the action string
with the prefix: "TO FIX:" . The action string is not
limited to a specific size.
An identifier that references on-line documentation for the message.
Suggested usage is that tag includes the
label and a unique identifying number. A sample tag is
The MSGVERB environment variable (for message verbosity) shall
determine for fmtmsg() which message components it
is to select when writing messages to standard error. The value of
MSGVERB shall be a colon-separated list of optional
keywords. 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() shall include that component
in the message when writing the message to standard error. If MSGVERB
does not include a keyword for a message component,
that component shall not be 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() shall select all components.
MSGVERB shall determine which components are selected for display
to standard error. All message components shall be
included in console messages.
The fmtmsg() function shall return one of the following values:
The function succeeded.
The function failed completely.
The function was unable to generate a message on standard error, but
The function was unable to generate a console message, but otherwise
The following sections are informative.
The following example of fmtmsg():
fmtmsg(MM_PRINT, "XSI:cat", MM_ERROR, "illegal option",
"refer to cat in user's reference manual", "XSI:cat:001")
produces a complete message in the specified message format:
XSI:cat: ERROR: illegal option
TO FIX: refer to cat in user's reference manual XSI:cat:001
When the environment variable MSGVERB is set as follows:
and Example 1 is used, fmtmsg() produces:
ERROR: illegal option
TO FIX: refer to cat in user's reference manual
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.
printf() , the Base Definitions volume of IEEE Std 1003.1-2001,
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at