Go by Example: String Formatting

Go offers excellent support for string formatting in the `printf` tradition. Here are some examples of common string formatting tasks.
	package main
	import "fmt" import "os"
	type point struct { x, y int }
	func main() {
Go offers several printing “verbs” designed to format general Go values. For example, this prints an instance of our `point` struct.	p := point{1, 2} fmt.Printf("%v\n", p)
If the value is a struct, the `%+v` variant will include the struct’s field names.	fmt.Printf("%+v\n", p)
The `%#v` variant prints a Go syntax representation of the value, i.e. the source code snippet that would produce that value.	fmt.Printf("%#v\n", p)
To print the type of a value, use `%T`.	fmt.Printf("%T\n", p)
Formatting booleans is straight-forward.	fmt.Printf("%t\n", true)
There are many options for formatting integers. Use `%d` for standard, base-10 formatting.	fmt.Printf("%d\n", 123)
This prints a binary representation.	fmt.Printf("%b\n", 14)
This prints the character corresponding to the given integer.	fmt.Printf("%c\n", 33)
`%x` provides hex encoding.	fmt.Printf("%x\n", 456)
There are also several formatting options for floats. For basic decimal formatting use `%f`.	fmt.Printf("%f\n", 78.9)
`%e` and `%E` format the float in (slightly different versions of) scientific notation.	fmt.Printf("%e\n", 123400000.0) fmt.Printf("%E\n", 123400000.0)
For basic string printing use `%s`.	fmt.Printf("%s\n", "\"string\"")
To double-quote strings as in Go source, use `%q`.	fmt.Printf("%q\n", "\"string\"")
As with integers as seen earlier, `%x` renders the string in base-16, with two output characters per byte of input.	fmt.Printf("%x\n", "hex this") fmt.Printf("% x\n", "hex with space")
To print a representation of a pointer, use `%p`.	fmt.Printf("%p\n", &p)
When formatting numbers you will often want to control the width and precision of the resulting figure. To specify the width of an integer, use a number after the `%` in the verb. By default the result will be right-justified and padded with spaces.	fmt.Printf("\|%6d\|%6d\|\n", 12, 345)
You can also specify the width of printed floats, though usually you’ll also want to restrict the decimal precision at the same time with the width.precision syntax.	fmt.Printf("\|%6.2f\|%6.2f\|\n", 1.2, 3.45)
To left-justify, use the `-` flag.	fmt.Printf("\|%-6.2f\|%-6.2f\|\n", 1.2, 3.45)
You may also want to control width when formatting strings, especially to ensure that they align in table-like output. For basic right-justified width.	fmt.Printf("\|%6s\|%6s\|\n", "foo", "b")
To left-justify use the `-` flag as with numbers.	fmt.Printf("\|%-6s\|%-6s\|\n", "foo", "b")
So far we’ve seen `Printf`, which prints the formatted string to `os.Stdout`. `Sprintf` formats and returns a string without printing it anywhere.	s := fmt.Sprintf("a %s", "string") fmt.Println(s)
You can format+print to `io.Writers` other than `os.Stdout` using `Fprintf`.	fmt.Fprintf(os.Stderr, "an %s\n", "error") }

$ go run string-formatting.go
{1 2}
{x:1 y:2}
main.point{x:1, y:2}
main.point
true
123
1110
!
1c8
78.900000
1.234000e+08
1.234000E+08
"string"
"\"string\""
6865782074686973
68 65 78 20 77 69 74 68 20 73 70 61 63 65
0x42135100
|    12|   345|
|  1.20|  3.45|
|1.20  |3.45  |
|   foo|     b|
|foo   |b     |
a string
an error

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