FMTMSG(3)                  POSIX Programmer's Manual                 FMTMSG(3)



PROLOG
       This manual page is part of the POSIX Programmer's Manual.  The OS
       implementation of this interface may differ (consult the corresponding
       OS manual page for details of OS behavior), or the interface may not be
       implemented on OS.

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: ""TTOOFIX:"..  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.

SEE ALSO
       fprintf()

       The Base Definitions volume of POSIX.1-2017, <fmtmsg.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1-2017, Standard for Information Technology --
       Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 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 http://www.opengroup.org/unix/online.html .

       Any typographical or formatting errors that appear in this page are
       most likely to have been introduced 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 .



IEEE/The Open Group                  2017                            FMTMSG(3)
