vlfmt(3C)

NAME

vlfmt − display error message in standard format and pass to logging and monitoring services

MT-LEVEL

MT-safe

SYNOPSIS

#include <stdarg.h>
#include <pfmt.h>
int vlfmt(FILE ∗stream, long flags, char ∗format, va_list ap);

DESCRIPTION

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 EXAMPLE section below shows their use with vlfmt().

The macro va_alist is used as the parameter list in a function definition as in the function called errlog() 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 errlog(). The remainting errlog() arguments, arg1, arg2, ..., are given to vlfmt() in the argument ap.

RETURN VALUE

Upon success, vlfmt() returns the number of bytes transmitted. Upon failure, it returns a negative value:

−1 write error to stream.

−2 cannot log and/or display at console.

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, ...)
{
    va_list ap;
    char ∗format;
    va_start(ap, );
    format = va_arg(ap, char ∗);
    (void) vlfmt(stderr, log_info|MM_ERROR, format, ap);
    va_end(ap);
    (void) abort();
}

NOTES

Since vlfmt() uses gettxt(3C), it is recommended that vlfmt() not be used.

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