fscanf() - C語言庫函式

C庫函式 int fscanf(FILE *stream, const char *format, ...) 從流中讀取的格式輸入。

宣告

以下是 fscanf() 函式的宣告。

int fscanf(FILE *stream, const char *format, ...)

引數

stream -- 這是一個檔案物件的標識流的指標。
format -- 這是C字串，其中包含一個或多個以下專案：空白字元，非空白字元和格式說明符。格式規範將 [=%[*][width][modifiers]type=], 詳細說明如下：

引數	描述
*	這是一個可選的星號表示該資料是從流中被讀取的，但忽略，即，它不會儲存在相應的引數。
width	這指定在當前讀出操作被讀取的最大字元數
modifiers	Specifies a size different from int (in the case of d, i and n), unsigned int (in the case of o, u and x) or float (in the case of e, f and g) for the data yiibaied by the corresponding additional argument: h : short int (for d, i and n), or unsigned short int (for o, u and x) l : long int (for d, i and n), or unsigned long int (for o, u and x), or double (for e, f and g) L : long double (for e, f and g)
type	的字元，指定將要讀取的資料的型別以及它是如何被讀取。請參閱下表。

fscanf型別說明：

型別	合格輸入	引數型別
c	Single character: Reads the next character. If a width different from 1 is specified, the function reads width characters and stores them in the successive locations of the array passed as argument. No null character is appended at the end.	char *
d	Decimal integer: Number optionally preceeded with a + or - sign	int *
e,E,f,g,G	Floating yiibai: Decimal number containing a decimal yiibai, optionally preceeded by a + or - sign and optionally folowed by the e or E character and a decimal number. Two examples of valid entries are -732.103 and 7.12e4	float *
o	OctalInteger:	int *
s	String of characters. This will read subsequent characters until a whitespace is found (whitespace characters are considered to be blank, newline and tab).	char *
u	Unsigned decimal integer.	unsigned int *
x,X	Hexadecimal Integer	int *

additional arguments -- 根據格式字串，函式可能會想到一系列的額外的引數，每個包含一個值，而不是插入的格式引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引數。

返回值

此函式返回成功匹配，分配的輸入專案的數量，它可以是少於提供了在一個早期的匹配失敗的情況下，甚至可以為零。

例子

下面的例子演示了如何使用fscanf() 函式。

#include <stdio.h>
#include <stdlib.h>


int main()
{
   char str1[10], str2[10], str3[10];
   int year;
   FILE * fp;

   fp = fopen ("file.txt", "w+");
   fputs("We are in 2012", fp);
   
   rewind(fp);
   fscanf(fp, "%s %s %s %d", str1, str2, str3, &year);
   
   printf("Read String1 |%s|
", str1 );
   printf("Read String2 |%s|
", str2 );
   printf("Read String3 |%s|
", str3 );
   printf("Read Integer |%d|
", year );

   fclose(fp);
   
   return(0);
}

讓我們編譯和執行上面的程式，這將產生以下結果：

Read String1 |We|
Read String2 |are|
Read String3 |in|
Read Integer |2012|