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vprintf() – C语言库函数

C库函数  int vprintf(const char *format, va_list arg)  发送格式化输出到stdout使用一个参数列表传递给它。

声明

以下是 vprintf() 函数的声明。

int vprintf(constchar*format, va_list arg)

参数

  • format — 这是包含文本的字符串被写入到缓冲。它可以包含嵌入的格式在随后的附加参数指定的值所取代的标签和格式化的要求。格式标签原型将是: %[flags][width][.precision][length]specifier, 详细说明如下:

修辞符 输出
c Character.
d or i Signed decimal integer
e Scientific notation (mantissa/exponent) using e character
E Scientific notation (mantissa/exponent) using E character
f Decimal floating yiibai
g Use the shorter of %e or %f.
G Use the shorter of %E or %f
o Signed octal
s String of characters
u Unsigned decimal integer
x Unsigned hexadecimal integer
X Unsigned hexadecimal integer (capital letters)
p Yiibaier address
n Nothing printed.
% Character.
flags 描述
Left-justify within the given field width; Right justification is the default (see width sub-specifier).
+ Forces to preceed the result with a plus or minus sign (+ or -) even for positive numbers. By default, only negative numbers are preceded with a – sign..
(space) If no sign is going to be written, a blank space is inserted before the value.
# Used with o, x or X specifiers the value is preceeded with 0, 0x or 0X respectively for values different than zero. Used with e, E and f, it forces the written output to contain a decimal yiibai even if no digits would follow. By default, if no digits follow, no decimal yiibai is written. Used with g or G the result is the same as with e or E but trailing zeros are not removed.
0 Left-pads the number with zeroes (0) instead of spaces, where padding is specified (see width sub-specifier).
width 描述
(number) Minimum number of characters to be printed. If the value to be printed is shorter than this number, the result is padded with blank spaces. The value is not truncated even if the result is larger.
* The width is not specified in the format string, but as an additional integer value argument preceding the argument that has to be formatted.
.precision 描述
.number For integer specifiers (d, i, o, u, x, X): precision specifies the minimum number of digits to be written. If the value to be written is shorter than this number, the result is padded with leading zeros. The value is not truncated even if the result is longer. A precision of 0 means that no character is written for the value 0. For e, E and f specifiers: this is the number of digits to be printed after de decimal yiibai. For g and G specifiers: This is the maximum number of significant digits to be printed. For s: this is the maximum number of characters to be printed. By default all characters are printed until the ending null character is encountered. For c type: it has no effect. When no precision is specified, the default is 1. If the period is specified without an explicit value for precision, 0 is assumed.
.* The precision is not specified in the format string, but as an additional integer value argument preceding the argument that has to be formatted.
length 描述
h The argument is interpreted as a short int or unsigned short int (only applies to integer specifiers: i, d, o, u, x and X).
l The argument is interpreted as a long int or unsigned long int for integer specifiers (i, d, o, u, x and X), and as a wide character or wide character string for specifiers c and s.
L The argument is interpreted as a long double (only applies to floating yiibai specifiers: e, E, f, g and G).
  • arg — 可变参数列表中的对象。这应该是初始化va_start宏在<stdarg>定义。

返回值

如果成功,则返回写入的字符的总数,否则返回一个负数。

例子

下面的例子演示了如何使用vprintf() 函数。

#include<stdio.h>#include<stdarg.h>voidWriteFrmtd(char*format,...){
va_list args;
va_start(args, format);
vprintf(format, args);
va_end(args);}int main (){WriteFrmtd("%d variable argument
",1);WriteFrmtd("%d variable %s
",2,"arguments");return(0);}

让我们编译和运行上面的程序,这将产生以下结果:

1 variable argument
2 variable arguments

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