Table of Contents

• Go by Example: String Formatting
• func Scan(a ...interface{}) (n int, err error)
• Printing Verbs(like %d, %v, etc)
• Scanning with Scanf, Fscanf, and the like

Go by Example: String Formatting tutorial

package main

import "fmt"

type point struct {
    x, y int
}

func main() {
    p := point{1, 2}
    fmt.Printf("00) %v\n", p)
    fmt.Printf("01) %+v\n", p)
    fmt.Printf("02) %#v\n", p)
    fmt.Printf("03) %T\n", p)
    fmt.Printf("04) %t\n", true)
    fmt.Printf("05) %d\n", 123)
    fmt.Printf("06) %b\n", 14)
    fmt.Printf("07) %c\n", 33)
    fmt.Printf("08) %x\n", 456)
    fmt.Printf("09) %f\n", 78.9)
    fmt.Printf("10) %e\n", 123400000.0)
    fmt.Printf("11) %E\n", 123400000.0)
    fmt.Printf("12) %s\n", "\"string\"")
    fmt.Printf("13) %q\n", "\"string\"")
    fmt.Printf("14) %x\n", "hex this")
    fmt.Printf("15) %p\n", &p)
    fmt.Printf("16) |%6d|%6d|\n", 12, 345)
    fmt.Printf("17) |%6.2f|%6.2f|\n", 1.2, 3.45)
    fmt.Printf("18) |%-6.2f|%-6.2f|\n", 1.2, 3.45)
    fmt.Printf("19) |%6s|%6s|\n", "foo", "b")
    fmt.Printf("20) |%-6s|%-6s|\n", "foo", "b")
}

00) {1 2}
01) {x:1 y:2}
02) main.point{x:1, y:2}
03) main.point
04) true
05) 123
06) 1110
07) !
08) 1c8
09) 78.900000
10) 1.234000e+08
11) 1.234000E+08
12) "string"
13) "\"string\""
14) 6865782074686973
15) 0xc0000180b0
16) |    12|   345|
17) |  1.20|  3.45|
18) |1.20  |3.45  |
19) |   foo|     b|
20) |foo   |b     |

s := fmt.Sprintf("a %s", "string")
fmt.Println(s)
fmt.Fprintf(os.Stderr, "an %s\n", "error")

func Scan(a ...interface{}) (n int, err error) reference

• Reads from standard input
• Stores successive space-separated values into successive arguments.
• Newlines count as space.
• Returns the number of items successfully scanned.
• If that is less than the number of arguments, err will report why.

Printing Verbs(like %d, %v, etc) reference

Scanning with Scanf, Fscanf, and the like discussion

a verb introduced by the % character

• consumes and parses input;

A character other than %, space, or newline

• consumes exactly that input character, which must be present.

A newline with zero or more spaces before it

• consumes zero or more spaces in the input followed by a single newline or the end of the input.

A space following a newline in the format string

• consumes zero or more spaces in the input.

Otherwise, any run of one or more spaces

• consumes as many spaces as possible in the input

Space and newline related rules are quite complicated. A related discussion is here.

My overall understanding is:

• Simplify, use just a space for skipping whitespaces
• Use \n only when you are sure where \n comes in the input.