Generates all possible CSS hex colours

colours.go

package main

import (
	"encoding/hex"
	"os"
	"strconv"
)

func main() {
	f, err := os.OpenFile("colours.css", os.O_WRONLY, 0600)
	if err != nil {
		panic(err)
	}

	defer f.Close()

	_, err = f.WriteString("hex {")
	if err != nil {
		panic(err)
	}
	for r := 0; r <= 255; r++ {
		rHex := getHex(r)
		for g := 0; g <= 255; g++ {
			gHex := getHex(g)
			for b := 0; b <= 255; b++ {
				bHex := getHex(b)
				formatted := "color: #" + rHex + gHex + bHex

				_, err := f.Write([]byte(formatted))
				if err != nil {
					panic(err)
				}
			}
		}
	}
	_, err = f.WriteString("}")
	if err != nil {
		panic(err)
	}
}

func getHex(num int) string {
	hexColour := hex.EncodeToString([]byte(strconv.Itoa(num)))
	if len(hexColour) == 1 {
		hexColour = "0" + hexColour
	}
	return hexColour
}

Current benchmarks have the time set to ~17 seconds writing to an SSD, and ~10 seconds on a ramdisk/tmpfs. The biggest bottleneck is definitely disk speed, followed closely by the getHex() function. Pretty sure that could be greatly optimized, just not sure how yet.

Version by @spoopy on Discord

package main

import (
	"fmt"
	"os"
	"strings"
)

func main() {
	f, err := os.OpenFile("colours.css", os.O_WRONLY, 0600)
	if err != nil {
		panic(err)
	}

	defer f.Close()

	var sb strings.Builder
	_, err = sb.WriteString("hex {")
	if err != nil {
		panic(err)
	}
	// 16777215 is FFFFFF in hex
	max := 16777215
	for i := 0; i <= max; i++ {
		_, err := fmt.Fprintf(&sb, "color: #%06X;\n", i)
		if err != nil {
			panic(err)
		}
	}
	_, err = sb.WriteString("}")
	if err != nil {
		panic(err)
	}
	_, err = f.WriteString(sb.String())
	if err != nil {
		panic(err)
	}
}

< 3 seconds on ramdisk