vprintf.3s

来自「<B>Digital的Unix操作系统VAX 4.2源码</B>」· 3S 代码 · 共 91 行

.\" SCCSID: @(#)vprintf.3s	8.1	9/11/90
.TH vprintf 3s
.SH Name
vprintf, vfprintf, vsprintf \- print formatted output of a varargs argument list
.SH Syntax
.B "#include <stdio.h>"
.br
.B "#include <varargs.h>"
.PP
.B "int vprintf (format, ap)
.br
.B "char \(**format;"
.br
.B "va_list ap;
.PP
.B "int vfprintf (stream, format, ap)
.br
.SM
.B FILE
.B \(**stream;
.br
.B "char \(**format;"
.br
.B "va_list ap;
.PP
.B "int vsprintf (s, format, ap)
.br
.B "char \(**s, \(**format;"
.br
.B "va_list ap;
.SH Description
.NXR "vprintf subroutine"
.NXR "vfprintf subroutine"
.NXA "printf subroutine" "vprintf subroutine"
.NXA "varargs subroutine" "vprintf subroutine"
.NXR "formatted output" "printing from argument list"
The
.PN vprintf ,
.PN vfprintf ,
and
.PN vsprintf
routines are the same as
.PN printf ,
.PN fprintf ,
and
.PN sprintf ,
respectively,
except that instead of being called with a variable number of 
arguments, they are called with an argument list as defined
by 
.MS varargs 3 .
.SH Examples
.NXR(e) "vprintf subroutine" "writing an error routine and"
The following demonstrates how 
.PN vfprintf
could be used
to write an error routine.
.EX 0
#include <stdio.h>
#include <varargs.h>
	.
	.
	.
/\(**
 \(**   error should be called like
 \(**        error(function_name, format, arg1, arg2...);
 \(**/
/\(**VARARGS0\(**/
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( );
}
.EE
.SH See Also
varargs(3)