Tribblix: manual page: vlfmt.3c

VLFMT(3C) Standard C Library Functions VLFMT(3C)

NAME

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

SYNOPSIS

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

int vlfmt(FILE *stream, long flag, const char *format, va_list ap);

DESCRIPTION

The vlfmt() function is identical to lfmt(3C), except that it is
called with an argument list as defined by <stdarg.h>.

The <stdarg.h> header defines the type va_list and a set of macros
for advancing through a list of arguments whose number and types may
vary. The ap argument is of type va_list. This argument is used with
the <stdarg.h> macros va_start(), va_arg(), and va_end(). See
stdarg(3EXT). The example in the EXAMPLES section below demonstrates
their use with vlfmt().

RETURN VALUES

Upon successful completion, vlfmt() returns the number of bytes
transmitted. Otherwise, -1 is returned if there was a write error to
stream, or -2 is returned if unable to log and/or display at console.

EXAMPLES

Example 1: Use of vlfmt() to write an errlog()routine.

The following example demonstrates how vlfmt() could be used to write
an errlog() routine. The va_alist() macro is used as the parameter
list in a function definition. The va_start(ap, ...) call, where ap
is of type va_list, must be invoked 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 atype argument 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
remaining errlog() arguments (arg1, arg2, ...) are passed to vlfmt()
in the argument ap.

#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();
}

USAGE

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

ATTRIBUTES