fscanf() - C語言庫函數

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

聲明

以下是 fscanf() 函數的聲明。

int fscanf(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，其中包含一個或多個以下項目：空白字符，非空白字符和格式說明符。格式規範將 [=%[*][width][modifiers]type=], 詳細說明如下：

參數

描述

*

這是一個可選的星號表示該數據是從流中被讀取的，但忽略，即，它不會存儲在相應的參數。

width

這指定在當前讀出操作被讀取的最大字符數

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

的字符，指定將要讀取的數據的類型以及它是如何被讀取。請參閱下表。

fscanf類型說明：

類型

合格輸入

參數類型

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

此函數返回成功匹配，分配的輸入項目的數量，它可以是少於提供了在一個早期的匹配失敗的情況下，甚至可以爲零。

例子

下面的例子演示瞭如何使用fscanf() 函數。

#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); }

讓我們編譯和運行上面的程序，這將產生以下結果：

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