GO by example, part 5

5-go-by-example/48-string-.formatting.go

@@ -0,0 +1,82 @@
+package main
+
+import (
+	"fmt"
+	"os"
+)
+
+type point struct {
+	x, y int
+}
+
+// common string formatting tasks
+func main() {
+	// prints an instance of point struct
+	p := point{1, 2}
+	fmt.Printf("struct1: %v\n", p)
+
+	// the %+v variant will include the struct’s field names
+	fmt.Printf("struct2: %+v\n", p)
+
+	// the %#v variant prints a Go syntax representation of the value
+	fmt.Printf("struct3: %#v\n", p)
+
+	// the %T variant prints the type of a value
+	fmt.Printf("type: %T\n", p)
+
+	// formatting booleans straight-forward
+	fmt.Printf("bool: %t\n", true)
+
+	// use %d for standard, base-10 formatting
+	fmt.Printf("int: %d\n", 123)
+
+	// prints a binary representation
+	fmt.Printf("bin: %b\n", 14)
+
+	// prints the character corresponding to the given integer
+	fmt.Printf("char: %c\n", 33)
+
+	// %x provides hex encoding
+	fmt.Printf("hex: %x\n", 456)
+
+	// decimal formatting use %f
+	fmt.Printf("float1: %f\n", 78.9)
+
+	// %e and %E format the float in (different versions of) scientific notation
+	fmt.Printf("float2: %e\n", 123400000.0)
+	fmt.Printf("float3: %E\n", 123400000.0)
+
+	// basic string printing use %s
+	fmt.Printf("str1: %s\n", "\"string\"")
+
+	// to double-quote strings use %q
+	fmt.Printf("str2: %q\n", "\"string\"")
+
+	// %x renders the string in base-16, with two output characters per byte of input
+	fmt.Printf("str3: %x\n", "hex this")
+
+	// use %p to print a representation of a pointer
+	fmt.Printf("pointer: %p\n", &p)
+
+	// to specify the width of an integer, use a number after the % in the verb
+	fmt.Printf("width1: |%6d|%6d|\n", 12, 345)
+
+	// to specify the width of printed floats
+	fmt.Printf("width2: |%6.2f|%6.2f|\n", 1.2, 3.45)
+
+	// to left-justify, use the - flag
+	fmt.Printf("width3: |%-6.2f|%-6.2f|\n", 1.2, 3.45)
+
+	// specify width when formatting strings
+	fmt.Printf("width4: |%6s|%6s|\n", "foo", "b")
+
+	// and left-justify strings with - too
+	fmt.Printf("width5: |%-6s|%-6s|\n", "foo", "b")
+
+	// Sprintf formats and returns a string without printing it anywhere
+	s := fmt.Sprintf("sprintf: a %s", "string")
+	fmt.Println(s)
+
+	// format+print to io.Writers other than os.Stdout using Fprintf
+	fmt.Fprintf(os.Stderr, "io: an %s\n", "error")
+}