说明：本文不适合新手学习，适合用来做参考。本文参考有其他博客的内容，不过年代久远已经忘记了，在此感谢各位博主！
scanf函数
用 法：int scanf(char *format[,argument,...]); //scanf()函数是通用终端格式化输入函数，它从标准输入设备(键盘) 读取输入的信息。可以读入任何固有类型的数据并自动把数值变换成适当的机内格式。
调用格式： scanf("<格式化字符串>"，<地址表>); // scanf()函数返回成功赋值的数据项数，出错时则返回EOF。
其控制串由三类字符构成：1、格式化说明符；2、空白符；3、非空白符；
1）格式化说明符
| 格式字符 | 说明 |
| %a、%A | 读入一个浮点值(仅C99有效) |
|
%f 、 %F、%e、
%E、%g 、%G
|
读入一个浮点数
|
| %c、%C | 读入一个字符 |
| %d | 读入十进制整数 |
| %s | 读入一个字符串 |
| %p | 读入一个指针 |
| %u |
读入一个无符号十进制整数
|
| %n | 至此已读入值的等价字符数 |
| %[] | 扫描字符集合 |
| %% | 读%符号 |
| %o | 读入八进制整数 |
| %x 、%X | 读入十六进制整数 |
| %i | 读入十进制，八进制，十六进制整数 |
2）空白字符
空白字符会使scanf()函数在读操作中略去输入中的一个或多个空白字符，空白符可以是space,tab,newline等等，直到第一个非空白符出现为止。
3）非空白字符
一个非空白字符会使scanf()函数在读入时剔除掉与这个非空白字符相同的字符。
fscanf函数
A format specifier for fscanf follows this prototype: % [*][width][length]specifier
The format specifier contain sub-specifiers: asterisk (*), width and length (in that order), which are optional and follow these specifications:
Where the specifier character at the end is the most significant component, since it defines which characters are extracted, their interpretation and the type of its corresponding argument:
Except for n, at least one character shall be consumed by any specifier. Otherwise the match fails, and the scan ends there.
| sub-specifier | description |
|---|---|
| * | An optional starting asterisk indicates that the data is to be read from the stream but ignored (i.e. it is not stored in the location pointed by an argument). 注：加上*可将该位置数据忽略 |
| width | Specifies the maximum number of characters to be read in the current reading operation (optional). 注：比如填入7.3,表示整数部分宽度为7，小数部分只读到第3位；也可以不填，不填则将对应数据不带舍入地读入 |
| length | One of hh, h, l, ll, j, z, t, L (optional). This alters the expected type of the storage pointed by the corresponding argument (see the last table). |
| specifier | Description | Characters extracted |
|---|---|---|
| i, u | Integer | Any number of digits, optionally preceded by a sign (+ or -). Decimal digits assumed by default (0-9), but a 0 prefix introduces octal digits (0-7), and 0x hexadecimal digits (0-f). |
| d | Decimal integer （十进制数） |
Any number of decimal digits (0-9), optionally preceded by a sign (+ or -). |
| o | Octal integer | Any number of octal digits (0-7), optionally preceded by a sign (+ or -). |
| x | Hexadecimal integer (16进制数) | Any number of hexadecimal digits (0-9, a-f, A-F), optionally preceded by 0x or 0X, and all optionally preceded by a sign (+ or -). |
| f, e, g | Floating point number (浮点数) |
A series of decimal digits, optionally containing a decimal point, optionally preceeded by a sign (+ or -) and optionally followed by the e or E character and a decimal integer (or some of the other sequences supported by strtod). Implementations complying with C99 also support hexadecimal floating-point format when preceded by 0x or 0X. |
| a | ||
| c | Character | The next character. If a width other than 1 is specified, the function reads exactlywidth characters and stores them in the successive locations of the array passed as argument. No null character is appended at the end. |
| s | String of characters | Any number of non-whitespace characters, stopping at the first whitespacecharacter found. A terminating null character is automatically added at the end of the stored sequence. |
| p | Pointer address | A sequence of characters representing a pointer. The particular format used depends on the system and library implementation, but it is the same as the one used to format %p in fprintf. |
| [characters] | Scanset | Any number of the characters specified between the brackets. A dash (-) that is not the first character may produce non-portable behavior in some library implementations. |
| [^characters] | Negated scanset | Any number of characters none of them specified as characters between the brackets. |
| n | Count | No input is consumed. The number of characters read so far from stream is stored in the pointed location. |
| % | % | A % followed by another % matches a single %. |
This is a chart showing the types expected for the corresponding arguments where input is stored (both with and without a length sub-specifier):(length放在specifiers前会产生不同的效果，更具体。也可以选择不使用)
| specifiers | |||||||
|---|---|---|---|---|---|---|---|
| length | d i | u o x | f e g a | c s [] [^] | p | n | |
| (none) | int* | unsigned int* | float* | char* | void** | int* | |
| hh | signed char* | unsigned char* | signed char* | ||||
| h | short int* | unsigned short int* | short int* | ||||
| l | long int* | unsigned long int* | double* | wchar_t* | long int* | ||
| ll | long long int* | unsigned long long int* | long long int* | ||||
| j | intmax_t* | uintmax_t* | intmax_t* | ||||
| z | size_t* | size_t* | size_t* | ||||
| t | ptrdiff_t* | ptrdiff_t* | ptrdiff_t* | ||||
| L | long double* | ||||||
