vprintf(S)                     6 January 1993                     vprintf(S)


 Name

    vprintf, vfprintf, vsprintf - print formatted output of a varargs
    argument list

 Syntax


    cc  . . .  -lc


    #include  <stdio.h>
    #include  <varargs.h>

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

    int vfprintf (stream, format, ap)
    FILE *stream;
    const char *format;
    va_list ap;

    int vsprintf (s, format, ap)
    char *s;
    const char *format;
    va_list ap;


 Description

    The vprintf, vfprintf, and vsprintf functions are the same as printf,
    fprintf, and sprintf respectively, except that instead of being called
    with a variable number of arguments, they are called with an argument
    list as defined by varargs(S).

 Example

    The following demonstrates the use of vfprintf to write an error routine.


       #include  <stdio.h>
       #include  <varargs.h>
               ...
       /*
        *      error should be called by:
        *      error(function_name, format, arg1, arg2...);  */

               /*VARARGS*/
       void
       error(va_alist)
       /* Note that the function_name and format arguments cannot be
        *  separately declared because of the definition of varargs. */
       va_dcl
       {
               va_list args;
               char *fmt;

               va_start(args);
               /* print out name of function causing error */
               (void)fprintf(stderr, "ERROR in %s: ", va_arg(args, char *));
               fmt = va_arg(args, char *);
               /* print out remainder of message */
               (void)vfprintf(stderr, fmt, args);
               va_end(args);
               (void)abort( );
       }


 See also

    printf(S), varargs(S)

 Standards conformance

    vfprintf, vprintf and vsprintf are conformant with:

    AT&T SVID Issue 2;
    X/Open Portability Guide, Issue 3, 1989;
    and ANSI X3.159-1989 Programming Language -- C.