C库类 的 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。
intfscanf(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#includeintmain(){charstr1[10],str2[10],str3[10];intyear;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|