vprintf()

Write formatted output to standard output (varargs)

Synopsis:

#include <stdio.h>
#include <stdarg.h>

int vprintf( const char* format, 
             va_list arg );

Arguments:

format: A string that specifies the format of the output. The formatting string determines what additional arguments you need to provide. For more information, see printf().
arg: A variable-argument list of the additional arguments, which you must have initialized with the va_start() macro.

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

Description:

The vprintf() function writes output to the file stdout, under control of the argument format.

The vprintf() function is a “varargs” version of printf().

Returns:

The number of characters written, or a negative value if an output error occurred (errno is set).

Examples:

Use vprintf() in a general error message routine:

#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>

void errmsg( const char* format, ... )
  {
    va_list arglist;

    printf( "Error: " );
    va_start( arglist, format );
    vprintf( format, arglist );
    va_end( arglist );
  }

int main( void )
  {
    errmsg( "%s %d %s", "Failed", 100, "times" );
    return EXIT_SUCCESS;
  }

Classification:

ANSI, POSIX 1003.1

Safety:
Cancellation point	No
Interrupt handler	No
Signal handler	No
Thread	Yes