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fscanf() – C语言库函数

C库函数 int fscanf(FILE *stream, const char *format, …) 从流中读取的格式输入。

声明

以下是 fscanf() 函数的声明。

int fscanf(FILE *stream,constchar*format,...)

参数

  • stream — 这是一个文件对象的标识流的指针。

  • format — 这是C字符串,其中包含一个或多个以下项目:空白字符,非空白字符和格式说明符。格式规范将 [=%[*][width][modifiers]type=], 详细说明如下:

参数 描述
* 这是一个可选的星号表示该数据是从流中被读取的,但忽略,即,它不会存储在相应的参数。
width 这指定在当前读出操作被读取的最大字符数
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,指定将要读取的数据的类型以及它是如何被读取。请参阅下表。

fscanf类型说明:

类型 合格输入 参数类型
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 — 根据格式字符串,函数可能会想到一系列的额外的参数,每个包含一个值,而不是插入的格式参数中指定的标记每个%,如果有的话。应该有相同数量的%预期值的标签的数量的这些参数。

返回值

此函数返回成功匹配,分配的输入项目的数量,它可以是少于提供了在一个早期的匹配失败的情况下,甚至可以为零。

例子

下面的例子演示了如何使用fscanf() 函数。

#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);}

让我们编译和运行上面的程序,这将产生以下结果:

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

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