c detailed explanation of formatted input and output

The content after the% sign in the standardized input-output function has always been a mystery. Try to add up here. The parts that can be placed in the two functions are as follows:

printf() %[flags][width][.prec][hlL]type
scanf() %[flags]type

scanf() is simpler.

printf()

1 flag

flag	meaning
-	Align left
+	Put a sign in front (+ or -)
(space)	Positive number left blank
0	0 padding
#	Add identifiers 0x, 0 before hexadecimal and octal respectively

2 width

width	meaning
number	Minimum number of characters (length of the entire output)
*	The next parameter is the number of characters
.number	The number of digits after the decimal point
.*	The next parameter is the number of digits after the decimal point

3 .pre

.pre	meaning
.number	The number of digits after the decimal point
.*	The next parameter is the number of digits after the decimal point

printf("%- 6d\n",123);// - 左对齐， 整数前填充空格，， 输出6位 ，  
 123
printf("%+06d\n",-123); // 加符号， 0填充，。
-00123
printf("%+08.2f\n",123.1); // 加符号， 0填充， 共八个字符， 小数点后2位， 输出浮点型。
+0123.10
printf("%#+08.2x\n",12); // 添加进制标识符
    0x0c

Don't add-the default is right alignment. Obviously, 0 padding cannot be used after left alignment. The order of grammars at the same level is irrelevant.

4 modifier

Type modification	meaning
hh	Single byte
h	short
l	long
ll	long
L	long doubel

5 Type

Types of	meaning
i or d	int
u	unsigned int
O	Octal
x	Hexadecimal
X	Hexadecimal for uppercase letters
f or F	float , 6
e or E	index
g	float
G	float
a or A	Hexadecimal floating point
c	char
s	String
p	pointer
n	Number of outputs or outputs

int num = 0; 
printf("hello world%n\n",&num); //%n的使用， 本地编译器不能使用%n, 在线编译器可以
printf("%d\n",num);
// 输出 
hello world
11

scanf()

1 scanf

flag	meaning
*	jump over
number	Maximum number of characters
hh	char
h	short
l	long, double
ll	long long
L	long double

2 scanf

type	meaning
d	int
i	Integer, may be hexadecimal or octal
u	unsigned int
O	Octal
x	Hexadecimal
a,e,f,g	float
c	char
s	String
[…]	Allowed characters
p	pointer

The return value of printf() and scanf()

prinff() returns the number of characters output
scanf() returns the number of items input