Go to main content

man pages section 3: Basic Library Functions

Exit Print View

Updated: Wednesday, July 27, 2022



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


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

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


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(3EXT). The example in the EXAMPLES section below demonstrates their use with vpfmt().

Return Values

Upon successful completion, vpfmt() returns the number of bytes transmitted. Otherwise, −1 is returned if there was a write error to stream.


Example 1 Use of vpfmt() to write an error routine.

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.

#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);
        (void) abort();


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


See attributes(7) for descriptions of the following attributes:


See Also

gettxt(3C), pfmt(3C), stdarg(3EXT), attributes(7)