Standards
Standards / Extensions |
C or C++ |
Dependencies |
XPG4.2
Single UNIX Specification, Version 3
|
both |
|
Format
#define _XOPEN_SOURCE_EXTENDED 1
#include <fmtmsg.h>
int fmtmsg(long classification, const char *label, int severity,
const char *text, const char *action, const char *tag);
General description
The fmtmsg()
function can be used to display messages in a specified format instead
of the traditional printf() function.
Based on a message's
classification component, fmtmsg() writes 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 identifiers from the following groups of major classifications
and subclassifications. 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 will 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. The constant __MM_MXLABELLN defines the
maximum length of label.
- 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.
- Other
- provides an unknown severity. Produce the string “SV=n”, where
n is the severity value specified.
- 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:
“TO FIX:”. 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 constant __MM_MXTAGLN defines
the maximum length of tag.
The MSGVERB environment variable (for message
verbosity) tells fmtmsg() which message components it is to select
when writing messages to standard error. The value of MSGVERB is
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() includes 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 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.
MSGVERB
affects only which components are selected for display to standard
error. All message components are included in console messages.
Returned value
fmtmsg() returns one of
the following values:
- Value
- Description
- MM_OK
- The function succeeded.
- MM_NOCON
- The function was unable to generate a console message, but otherwise
succeeded.
- MM_NOMSG
- The function was unable to generate a message on standard error,
but otherwise succeeded.
- MM_NOTOK
- The function failed completely.
Examples
The following is an
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
The
following is another example when the environment variable MSGVERB
is set.
export MSGVERB=severity:text:action
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:
ERROR: illegal option
TO FIX: refer to cat in user's reference manual