vprintf.3int

来自「<B>Digital的Unix操作系统VAX 4.2源码</B>」· 3INT 代码 · 共 143 行

.TH vprintf 3int
.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 (
.IR format , 
.I ap
.B )
.br
.B char 
.IR *format ;
.br
.B va list 
.IR ap ;
.PP
.B int vfprintf (
.IR stream , 
.IR format , 
.I ap
.B )
.br
.B FILE
.IR *stream ;
.br
.B char 
.IR *format ;
.br
.B va list 
.IR ap ;
.PP
.B int vsprintf (
.IR s , 
.IR format , 
.I ap
.B )
.br
.B char 
.IR *s , 
.IR *format ;
.br
.B va list 
.IR ap ;
.SH Description
.NXR "vprintf subroutine"
.NXR "vfprintf subroutine"
.NXR "vsprintf subroutine"
The international functions 
.PN vprintf , 
.PN vfprintf , 
and 
.PN vsprintf 
are similar to the 
.PN vprintf
standard I/O functions. 
.PP
Likewise, the vprintf functions are similar to the printf functions 
except they are called with an argument list as defined by 
.PN varargs
instead of with a variable number of arguments.
.PP
The international functions allow you to use the 
.I %digit$ 
conversion character in place of the 
.I % 
character  you use in the standard I/O functions.  The digit is a
decimal digit 
.I n 
from 1 to 9.  The international functions apply conversions to the 
.I nth 
argument in the argument list, rather than to the next unused argument.
.PP 
You can use the 
.I %
conversion character in the international functions.  However, you cannot mix 
the 
.I %
conversion character with the 
.I %digit$ 
conversion character in a single call.
.PP
You can indicate a field width or precision by an asterisk
(*) instead of a digit string in format strings containing
the 
.I % 
conversion character. If you use an asterisk, you can
supply an integer 
.I arg
that specifies the field width or precision.  In format strings containing the 
.I %digit$
conversion character, you can indicate field width or precision by the
sequence \fI*digit$\fP.
You use a decimal digit from 1 to 9 to indicate which argument contains an 
integer that specifies the field width or precision.
.PP
The conversion characters and their meanings are identical to 
.PN printf .
.PP
You must use each digit argument at least once.
.SH Examples
.EX
#include <stdio.h>
#include <varargs.h>

main()
{
char *function_name = "vpr";
char *arg1 = "hello world";
int arg2 = 2;
char *arg3 = "study";

char *i18nfmt = "%1$s %3$d\\n";

test(function_name, i18nfmt, arg1, arg2, arg3);
}

test(va_alist)
va_dcl
{
va_list args;
char *fmt;
char string[1024];

va_start(args);

(void)printf("function %s: ", va_arg(args, char *));

fmt = va_arg(args, char *);

(void)vprintf(fmt, args);

va_end(args);
}
.EE
.SH See Also 
setlocale(3), scanf(3int), printf(3s), printf(3int), vprintf(3s), 
putc(3s), scanf(3s), stdio(3s), varargs(3) 
.br
.I Guide to Developing International Software