lfmt(3C)

lfmt, vlfmt -- display error message in standard format and pass to logging and monitoring services

Synopsis

   #include <pfmt.h>
   
   int lfmt(FILE stream, long flags, char format, . . . / args /);
   

   #include <stdarg.h>
   #include <pfmt.h>
   

   int vlfmt(FILE stream, long flags, char format, va_list ap);

Description

lfmt

lfmt retrieves a format string from a locale-specific message database (unless MM_NOGET is specified) and uses it for printf style formatting of args. The output is displayed on stream. If stream is NULL, no output is displayed. lfmt encapsulates the output in the standard error message format (unless MM_NOSTD is specified, in which case the output is simply printf-like).

lfmt forwards its output to the logging and monitoring facility, even if stream is null. lfmt will also display the output on the console, with a date and time stamp, when MM_CONSOLE is specified (see below).

If the printf format string is to be retrieved from a message database, the format argument must have the following structure:

   [catalog:]msgnum:defmsg.

If MM_NOGET is specified, only the defmsg part must be specified.

catalog indicates the message database that contains the localized version of the format string. catalog must be limited to 14 characters. These characters must be selected from a set of all character values, excluding \0 (null) and the ASCII codes for / (slash) and ``:'' (colon).

msgnum must be a positive number that indicates the index of the string into the message database.

If catalog does not exist in the locale (specified by the last call to setlocale using the LC_ALL or LC_MESSAGES categories), or if the message number is out of bounds, lfmt attempts to retrieve the message from the C locale. If this second retrieval fails, lfmt uses the defmsg part of the format argument.

If catalog is omitted, lfmt attempts to retrieve the string from the default catalog specified by the last call to setcat. In this case, the format argument has the following structure:

   msgnum:defmsg.

lfmt outputs

   Message not found!!\n

as the format string if:

catalog is not a valid catalog name as defined above
no catalog is specified (either explicitly or via setcat)
msgnum is not a positive number
if no message could be retrieved from the message databases and defmsg was omitted

The flags determine the type of output (that is, whether the format should be interpreted as is or encapsulated in the standard message format), and the access to message catalogs to retrieve a localized version of format. The flags are composed of several groups, and can take the following values (one from each group):

Output format control

MM_NOSTD: do not use the standard message format, interpret format as a printf format. Only ``catalog access control flags'', ``console display control'', and ``logging information'' should be specified if MM_NOSTD is used; all other flags will be ignored.
MM_STD: output using the standard message format (default, value 0).

Catalog access control

MM_NOGET: do not retrieve a localized version of format. In this case, only the defmsg part of the format is specified.
MM_GET: retrieve a localized version of format, from the catalog, using msgnum as the index and defmsg as the default message (default, value 0).

Severity (standard message format only)

MM_HALT: generates a localized version of HALT.
MM_ERROR: generates a localized version of ERROR (default, value 0).
MM_WARNING: generates a localized version of WARNING.
MM_INFO: generates a localized version of INFO.

Additional severities can be defined. Add-on severities can be defined with number-string pairs with numeric values from the range [5-255], using addsev(3C). The numeric value ORed with other flags will generate the specified severity.

If the severity is not defined, lfmt uses the string SEV=N where N is replaced by the integer severity value passed in flags.

Multiple severities passed in flags will not be detected as an error. Any combination of severities will be summed and the numeric value will cause the display of either a severity string (if defined) or the string SEV=N (if undefined).

Action

MM_ACTION: specifies an action message. Any severity value is superseded and replaced by a localized version of TO FIX.

Console display control

MM_CONSOLE: display the message to the console in addition to the specified stream.
MM_NOCONSOLE: do not display the message to the console in addition to the specified stream (default, value 0).

Logging information

Major classification

identifies the source of the condition. Identifiers are:

MM_HARD: (hardware),
MM_SOFT: (software), and
MM_FIRM: (firmware).

Message source subclassification

identifies the type of software in which the problem is spotted. Identifiers are:

MM_APPL: (application),
MM_UTIL: (utility), and
MM_OPSYS: (operating system).

Standard error message format

lfmt displays error messages in the following format:

   label: severity: text

If no label was defined by a call to setlabel, the message is displayed in the format:

   severity: text

If lfmt is called twice to display an error message and a helpful action or recovery message, the output can look like:

   label: severity: text
   label: TO FIX: text

vlfmt

vlfmt is the same as lfmt except that instead of being called with a variable number of arguments, it is called with an argument list as defined by the stdarg.h header file.

The stdarg.h header file defines the type va_list and a set of macros for advancing through a list of arguments whose number and types may vary. The argument ap to vlfmt is of type va_list. This argument is used with the stdarg.h header file macros va_start, va_arg and va_end [see va_start, va_arg, and va_end in stdarg(5)]. The USAGE section below show their use.

The macro va_alist is used as the parameter list in a function definition as in the function called error in the example below. The macro

   va_start(ap, )

where ap is of type va_list, must be called before any attempt to traverse and access unnamed arguments. Calls to

   va_arg(ap, atype)

traverse the argument list. Each execution of va_arg expands to an expression with the value and type of the next argument in the list ap, which is the same object initialized by va_start. The argument atype is the type that the returned argument is expected to be. The va_end(ap) macro must be invoked when all desired arguments have been accessed. [The argument list in ap can be traversed again if va_start is called again after va_end.] In the example below, va_arg is executed first to

retrieve the format string passed to error. The remaining error arguments, arg1, arg2, . . ., are given to vlfmt in the argument ap.

Return values

On success, lfmt and vlfmt return the number of bytes transmitted. On failure, they return a negative value.

Errors

-1: write error to stream
-2: cannot log and/or display at console.

Usage

lftmt example 1

setlabel("UX:test");
lfmt(stderr, MM_ERROR|MM_CONSOLE|MM_SOFT|MM_UTIL,
"test:2:Cannot open file: %s\n", strerror(errno));

displays the message to ``stderr'' and to the console and makes it available for logging:

   UX:test: ERROR: Cannot open file: No such file or directory

lftmt example 2

setlabel("UX:test");
lfmt(stderr, MM_INFO|MM_SOFT|MM_UTIL,
"test:23:test facility is enabled\n");

displays the message to ``stderr'' and makes it available for logging:

   UX:test: INFO: test facility enabled

vlfmt example

The following demonstrates how vlfmt could be used to write an errlog routine:

   #include <pfmt.h>
   #include <stdarg.h>
   . . .
   /
       errlog should be called like
             errlog(log_info, format, arg1, ...);
    /
   void errlog(long log_info, const char format, ...)
   
   {
       va_list ap;
   

       va_start(ap, format);
       (void) vlfmt(stderr, log_info|MM_ERROR, format, ap);
       va_end(ap);
       (void) abort();
   }

References

addsev(3C), environ(5), fprintf(3S), gettxt(3C), lfmt(1), pfmt(1), setcat(3C), setlabel(3C), setlocale(3C), stdarg(5)