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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.

NAME

       fmtmsg — display a message in the specified format on standard error and/or a 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

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.

classification
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 console.)

Major Classifications
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).

Display Subclassifications
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.

Status Subclassifications
Indicates whether the application can recover from the condition. Identifiers are:
MM_RECOVER (recoverable) 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 string "HALT".

MM_ERROR Indicates that the application has detected a fault. Produces the string "ERROR".

MM_WARNING Indicates a condition that is out of the ordinary, 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 unspecified.

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 limited 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 "XSI:cat:146".

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.

RETURN VALUE

       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 otherwise succeeded.

ERRORS

       None.

       The following sections are informative.

EXAMPLES

        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:

               MSGVERB=severity:text:action

           and Example 1 is used, fmtmsg() produces:

               ERROR: illegal option
               TO FIX: refer to cat in user's reference manual

APPLICATION USAGE

       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.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

COPYRIGHT

       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 Electrical 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 .

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       during   the   conversion  of  the  source  files  to  man  page  format.  To  report  such  errors,  see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .