fprintf() - C語言庫函數
C庫函數 int fprintf(FILE *stream, const char *format, ...) 發送格式化輸出到一個流。
聲明
以下是聲明 fprintf() 函數的功能。
int fprintf(FILE *stream, const char *format, ...)
參數
stream -- 這是一個文件對象的標識流的指針。
format - 這是C字符串，其中包含的文字寫入流。它可以包含嵌入的格式在隨後的附加參數指定的值所取代的標籤和格式化所要求。格式標籤的原型是 %[flags][width][.precision][length]specifier, 如下列表所示：
指示符
輸出
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.
標識
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).
- additional arguments -- 根據格式字符串，函數可能會想到一系列的額外的參數，每個包含一個值，而不是插入的格式參數中指定的標記每個％，如果有的話。應該有相同數量的％預期值的標籤的數量的這些參數。
返回值
如果成功，返回寫入的字符的總數，否則則返回一個負數。
例子
下面的例子顯示fprintf() 函數功能的用法。
#include <stdio.h> #include <stdlib.h> int main() { FILE * fp; fp = fopen ("file.txt", "w+"); fprintf(fp, "%s %s %s %d", "We", "are", "in", 2012); fclose(fp); return(0); }
讓我們編譯和運行上面的程序，這將創建一個文件 file.txt 中包含以下內容：
We are in 2012