scanf格式说明符遵循以下原则：
%[*][width][length]specifier
| specifier | Description | Characters extracted |
|---|---|---|
| i | 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), and0x hexadecimal digits (0-f). Signed argument. |
| d or u | Decimal integer | Any number of decimal digits (0-9), optionally preceded by a sign (+ or -). d is for a signed argument, and u for an unsigned. |
| o | Octal integer | Any number of octal digits (0-7), optionally preceded by a sign (+ or -). Unsigned argument. |
| x | Hexadecimal integer | 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 -). Unsigned argument. |
| f, e, g | Floating point number | 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 exactly widthcharacters 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 whitespace character 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 %pin 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 stdin is stored in the pointed location. |
| % | % | A % followed by another % matches a single %. |