FMTMSG(3P) POSIX Programmer's Manual FMTMSG(3P)PROLOG
This manual page is part of the POSIX Programmer's Manual. The Linux
implementation of this interface may differ (consult the corresponding
Linux manual page for details of Linux behavior), or the interface may
not be implemented on Linux.
NAMEfmtmsg — display a message in the specified format on standard error
and/or a system console
int fmtmsg(long classification, const char *label, int severity,
const char *text, const char *action, const char *tag);
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 sub‐
class identifiers may be used so that messages can be dis‐
played to both standard error and the system console.)
Identifies the source of the condition. Identifiers
are: MM_HARD (hardware), MM_SOFT (software), and
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. Iden‐
tifiers are: MM_PRINT to display the message on the
standard error stream, MM_CONSOLE to display the mes‐
sage on the system console. One or both identifiers
may be used.
Indicates whether the application can recover from
the condition. Identifiers are: MM_RECOVER (recover‐
able) and MM_NRECOV (non-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 is two
fields separated by a <colon>. The first field is up to 10
bytes, the second is up to 14 bytes.
severity Indicates the seriousness of the condition. Identifiers for
the levels of severity are:
MM_HALT Indicates that the application has encountered
a severe fault and is halting. Produces the
MM_ERROR Indicates that the application has detected a
fault. Produces the string "ERROR".
MM_WARNING Indicates a condition that is out of the ordi‐
nary, that might be a problem, and should be
watched. Produces the string "WARNING".
MM_INFO Provides information about a condition that is
not in error. Produces the string "INFO".
MM_NOSEV Indicates that no severity level is supplied
for the message.
text 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
action Describes the first step to be taken in the error-recovery
process. The fmtmsg() function precedes the action string
with the prefix: "TOFIX:". The action string is not lim‐
ited to a specific size.
tag 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 deter‐
mine 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
The fmtmsg() function shall return one of the following values:
MM_OK The function succeeded.
MM_NOTOK The function failed completely.
MM_NOMSG The function was unable to generate a message on standard
error, but otherwise succeeded.
MM_NOCON The function was unable to generate a console message, but
The following sections are informative.
1. 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
2. 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 mes‐
sages generated by an application by using the null value of the argu‐
ment for that component.
The Base Definitions volume of POSIX.1‐2008, <fmtmsg.h>
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
cal and Electronics Engineers, Inc and The Open Group. (This is
POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) 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 http://www.unix.org/online.html .
Any typographical or formatting errors that appear in this page are
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IEEE/The Open Group 2013 FMTMSG(3P)