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| Standard C Library Functions | vpfmt(3C) |
| | vpfmt - display error message in standard format and pass to logging and monitoring services |
SYNOPSIS
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#include <pfmt.h>
#include <stdarg.h> int vpfmt(FILE *stream, long flag, const char *format, va_list ap); |
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The vpfmt() function is identical to pfmt(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(3HEAD). The example in
the EXAMPLES section below demonstrates their use with vpfmt().
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Upon successful completion, vpfmt() returns the number of bytes transmitted. Otherwise, -1 is returned if there was a write error to stream.
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| | Example 1. Use of vpfmt to write an error routine.
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The following example demonstrates how vpfmt() could be used to write an error() 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 error(). The remaining error() arguments (arg1, arg2, ...) are passed to vpfmt() in the argument ap.
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#include <pfmt.h>
#include <stdarg.h>
/*
* error should be called like
* error(format, arg1, ...);
*/
void error(...)
{
va_list ap;
char *format;
va_start(ap, );
format = va_arg(ap, char *);
(void) vpfmt(stderr, MM_ERROR, format, ap);
va_end(ap);
(void) abort();
}
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Since vpfmt() uses gettxt(3C), it is recommended that vpfmt() not be used.
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See attributes(5) for descriptions of the following
attributes:
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
| MT-Level | MT-Safe |
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