publish ch1/...

ch1/dup1/main.go

@@ -0,0 +1,31 @@
+// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+
+// See page 8.
+//!+
+
+// Dup1 prints the text of each line that appears more than
+// once in the standard input, preceded by its count.
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+)
+
+func main() {
+	counts := make(map[string]int)
+	input := bufio.NewScanner(os.Stdin)
+	for input.Scan() {
+		counts[input.Text()]++
+	}
+	// NOTE: ignoring potential errors from input.Err()
+	for line, n := range counts {
+		if n > 1 {
+			fmt.Printf("%d\t%s\n", n, line)
+		}
+	}
+}
+
+//!-

ch1/dup2/main.go

@@ -0,0 +1,48 @@
+// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+
+// See page 10.
+//!+
+
+// Dup2 prints the count and text of lines that appear more than once
+// in the input.  It reads from stdin or from a list of named files.
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+)
+
+func main() {
+	counts := make(map[string]int)
+	files := os.Args[1:]
+	if len(files) == 0 {
+		countLines(os.Stdin, counts)
+	} else {
+		for _, arg := range files {
+			f, err := os.Open(arg)
+			if err != nil {
+				fmt.Fprintf(os.Stderr, "dup2: %v\n", err)
+				continue
+			}
+			countLines(f, counts)
+			f.Close()
+		}
+	}
+	for line, n := range counts {
+		if n > 1 {
+			fmt.Printf("%d\t%s\n", n, line)
+		}
+	}
+}
+
+func countLines(f *os.File, counts map[string]int) {
+	input := bufio.NewScanner(f)
+	for input.Scan() {
+		counts[input.Text()]++
+	}
+	// NOTE: ignoring potential errors from input.Err()
+}
+
+//!-

ch1/dup3/main.go

@@ -0,0 +1,37 @@
+// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+
+// See page 12.
+
+// Dup3 prints the count and text of lines that appear more than once
+// in the named input files.
+//!+
+package main
+
+import (
+	"fmt"
+	"io/ioutil"
+	"os"
+	"strings"
+)
+
+func main() {
+	counts := make(map[string]int)
+	for _, filename := range os.Args[1:] {
+		data, err := ioutil.ReadFile(filename)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "dup3: %v\n", err)
+			continue
+		}
+		for _, line := range strings.Split(string(data), "\n") {
+			counts[line]++
+		}
+	}
+	for line, n := range counts {
+		if n > 1 {
+			fmt.Printf("%d\t%s\n", n, line)
+		}
+	}
+}
+
+//!-

ch1/echo1/main.go

@@ -0,0 +1,24 @@
+// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+
+// See page 4.
+//!+
+
+// Echo1 prints its command-line arguments.
+package main
+
+import (
+	"fmt"
+	"os"
+)
+
+func main() {
+	var s, sep string
+	for i := 1; i < len(os.Args); i++ {
+		s += sep + os.Args[i]
+		sep = " "
+	}
+	fmt.Println(s)
+}
+
+//!-

ch1/echo2/main.go

@@ -0,0 +1,24 @@
+// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+
+// See page 6.
+//!+
+
+// Echo2 prints its command-line arguments.
+package main
+
+import (
+	"fmt"
+	"os"
+)
+
+func main() {
+	s, sep := "", ""
+	for _, arg := range os.Args[1:] {
+		s += sep + arg
+		sep = " "
+	}
+	fmt.Println(s)
+}
+
+//!-

ch1/echo3/main.go

@@ -0,0 +1,20 @@
+// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+
+// See page 8.
+
+// Echo3 prints its command-line arguments.
+package main
+
+import (
+	"fmt"
+	"os"
+	"strings"
+)
+
+//!+
+func main() {
+	fmt.Println(strings.Join(os.Args[1:], " "))
+}
+
+//!-

ch1/fetch/main.go

@@ -0,0 +1,34 @@
+// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+
+// See page 16.
+//!+
+
+// Fetch prints the content found at a URL.
+package main
+
+import (
+	"fmt"
+	"io/ioutil"
+	"net/http"
+	"os"
+)
+
+func main() {
+	for _, url := range os.Args[1:] {
+		resp, err := http.Get(url)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "fetch: %v\n", err)
+			os.Exit(1)
+		}
+		b, err := ioutil.ReadAll(resp.Body)
+		resp.Body.Close()
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "fetch: reading %s: %v\n", url, err)
+			os.Exit(1)
+		}
+		fmt.Printf("%s", b)
+	}
+}
+
+//!-

ch1/fetchall/main.go

@@ -0,0 +1,49 @@
+// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+
+// See page 17.
+//!+
+
+// Fetchall fetches URLs in parallel and reports their times and sizes.
+package main
+
+import (
+	"fmt"
+	"io"
+	"io/ioutil"
+	"net/http"
+	"os"
+	"time"
+)
+
+func main() {
+	start := time.Now()
+	ch := make(chan string)
+	for _, url := range os.Args[1:] {
+		go fetch(url, ch) // start a goroutine
+	}
+	for range os.Args[1:] {
+		fmt.Println(<-ch) // receive from channel ch
+	}
+	fmt.Printf("%.2fs elapsed\n", time.Since(start).Seconds())
+}
+
+func fetch(url string, ch chan<- string) {
+	start := time.Now()
+	resp, err := http.Get(url)
+	if err != nil {
+		ch <- fmt.Sprint(err) // send to channel ch
+		return
+	}
+
+	nbytes, err := io.Copy(ioutil.Discard, resp.Body)
+	resp.Body.Close() // don't leak resources
+	if err != nil {
+		ch <- fmt.Sprintf("while reading %s: %v", url, err)
+		return
+	}
+	secs := time.Since(start).Seconds()
+	ch <- fmt.Sprintf("%.2fs  %7d  %s", secs, nbytes, url)
+}
+
+//!-

ch1/helloworld/main.go

@@ -1,7 +1,16 @@
+// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+
+// See page 1.
+
+// Helloworld is our first Go program.
+//!+
 package main
 
 import "fmt"
 
 func main() {
 	fmt.Println("Hello, 世界")
 }
+
+//!-

ch1/lissajous/main.go

@@ -0,0 +1,77 @@
+// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+
+// Run with "web" command-line argument for web server.
+// See page 13.
+//!+main
+
+// Lissajous generates GIF animations of random Lissajous figures.
+package main
+
+import (
+	"image"
+	"image/color"
+	"image/gif"
+	"io"
+	//!-main
+	"log"
+	//!+main
+	"math"
+	"math/rand"
+	//!-main
+	"net/http"
+	//!+main
+	"os"
+)
+
+var palette = []color.Color{color.White, color.Black}
+
+const (
+	whiteIndex = 0 // first color in palette
+	blackIndex = 1 // next color in palette
+)
+
+func main() {
+	//!-main
+	if len(os.Args) > 1 && os.Args[1] == "web" {
+		//!+http
+		handler := func(w http.ResponseWriter, r *http.Request) {
+			lissajous(w)
+		}
+		http.HandleFunc("/", handler)
+		//!-http
+		log.Fatal(http.ListenAndServe("localhost:8000", nil))
+		return
+	}
+	//!+main
+	lissajous(os.Stdout)
+}
+
+func lissajous(out io.Writer) {
+	const (
+		cycles  = 5     // number of complete x oscillator revolutions
+		res     = 0.001 // angular resolution
+		size    = 100   // image canvas covers [-size..+size]
+		nframes = 64    // number of animation frames
+		delay   = 8     // delay between frames in 10ms units
+	)
+	freq := rand.Float64() * 3.0 // relative frequency of y oscillator
+	anim := gif.GIF{LoopCount: nframes}
+	phase := 0.0 // phase difference
+	for i := 0; i < nframes; i++ {
+		rect := image.Rect(0, 0, 2*size+1, 2*size+1)
+		img := image.NewPaletted(rect, palette)
+		for t := 0.0; t < cycles*2*math.Pi; t += res {
+			x := math.Sin(t)
+			y := math.Sin(t*freq + phase)
+			img.SetColorIndex(size+int(x*size+0.5), size+int(y*size+0.5),
+				blackIndex)
+		}
+		phase += 0.1
+		anim.Delay = append(anim.Delay, delay)
+		anim.Image = append(anim.Image, img)
+	}
+	gif.EncodeAll(out, &anim) // NOTE: ignoring encoding errors
+}
+
+//!-main

ch1/server1/main.go

@@ -0,0 +1,26 @@
+// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+
+// See page 19.
+//!+
+
+// Server1 is a minimal "echo" server.
+package main
+
+import (
+	"fmt"
+	"log"
+	"net/http"
+)
+
+func main() {
+	http.HandleFunc("/", handler) // each request calls handler
+	log.Fatal(http.ListenAndServe("localhost:8000", nil))
+}
+
+// handler echoes the Path component of the request URL r.
+func handler(w http.ResponseWriter, r *http.Request) {
+	fmt.Fprintf(w, "URL.Path = %q\n", r.URL.Path)
+}
+
+//!-