Golang FMT format "placeholder"

This is a creation in Article, where the information may have evolved or changed.

This article is forwarded, the original address

Golang's FMT package implements formatted I/O functions, similar to the C printf and scanf.

# 定义示例类型和变量type Human struct {    Name string}var people = Human{Name:"zhangsan"}

Common placeholder

placeholder	Description	Example	Output
%v	The default format for the corresponding value.	Printf ("%v", people)	{Zhangsan}
%+v	Field names are added when the structure is printed	Printf ("%+v", people)	{Name:zhangsan}
% #v	The go syntax representation of the corresponding value	Printf ("#v", people)	Main. Human{name: "Zhangsan"}
%T	The go syntax for the type of the corresponding value	Printf ("%T", people)	Main. Human
%%	Literal percent-semicolon, not a placeholder for a value	PRINTF ("percent")	%

Boolean placeholder

placeholder	Description	Example	Output
%t	True or FALSE.	Printf ("%t", True)	True

Integer placeholders

placeholder	Description	Example	Output
%b	Binary representation	Printf ("%b", 5)	101
%c	The character represented by the corresponding Unicode code point	Printf ("%c", 0x4e2d)	In
%d	Decimal representation	Printf ("%d", 0x12)	18
%o	Octal representation	Printf ("%d", 10)	12
%q	Character literals surrounded by single quotes, safely escaped by go syntax	Printf ("%q", 0x4e2d)	In
%x	Hexadecimal representation, alphabetic form lowercase a-f	Printf ("%x", 13)	D
%x	Hexadecimal representation, uppercase a-f in alphabetic form	Printf ("%x", 13)	D
%u	Unicode format: u+1234, equivalent to "u+%04x"	Printf ("%u", 0x4e2d)	U+4e2d

Components of floating-point numbers and complex numbers (real and imaginary parts)

placeholder	Description	Example	Output
%b	The scientific notation of a power with no fractional part, exponential two, and StrConv. The formatfloat ' B ' conversion format is consistent. such as -123456p-78
%e	Scientific counting method, for example -1234.456e+78	Printf ("%e", 10.2)	1.020000e+01
%E	Scientific counting method, for example -1234.456E+78	Printf ("%e", 10.2)	1.020000E+01
%f	Have a decimal point but no index, for example 123.456	Printf ("%f", 10.2)	10.200000
%g	Select%e or%f to produce a more compact (no end 0) output, depending on the situation	Printf ("%g", 10.20)	10.2
%G	Select%E or%f to produce a more compact (no end 0) output, depending on the situation	Printf ("%G", 10.20+2i)	(10.2+2i)

String and byte slices

placeholder	Description	Example	Output
%s	Output string representation (string type or []byte)	Printf ("%s", []byte ("Go Language"))	Go language
%q	String surrounded by double quotes, safely escaped by go syntax	Printf ("%q", "Go Language")	"Go Language"
%x	Hex, lowercase letter, two characters per byte	Printf ("%x", "Golang")	676f6c616e67
%x	Hex, capital letter, two characters per byte	Printf ("%x", "Golang")	676f6c616e67

Pointer

placeholder	Description	Example	Output
%p	Hexadecimal representation, prefix 0x	Printf ("%p", &people)	0x4f57f0

Other marks

placeholder	Description	Example	Output
+	The positive and negative number of the total printed value; for%q (%+ Q) Ensure that only ASCII-encoded characters are output.	printf ("%+q", "Chinese")	"\u4e2d\u6587"
-
#	alternate format: Add a leading 0 (% #o) for octal	printf ("% #U", ' Medium ')	u+4e2d
"
0	padding leading 0 instead of spaces For numbers, this moves the fill to the sign after the

• Golang does not have a '%u ' dot, and if the integer is an unsigned type, it is printed as unsigned by default. The control format for

• Width and precision is in Unicode code points. The width is the minimum width of the area occupied by the value, and the precision is the number of digits after the decimal point. When the
  operand is of type int, the width and precision are available as characters ' * '.

• For%g/%g, the precision is the total number of all numbers, for example: 123.45,%.4g prints 123.5 (and%6.2f prints 123.45). The default precision for

• %e and%f is 6

• For most numeric types, the width is the minimum number of characters for the output and, if necessary, fills the formatted form with spaces.

• With a string type, with precision as the maximum number of characters to output, and truncated if necessary.