Add dir

dir/dir.go

@@ -0,0 +1,66 @@
+package dir
+
+import (
+	"fmt"
+	"io/fs"
+	"os"
+	"path/filepath"
+)
+
+func check(err error) {
+	if err != nil {
+		panic(err)
+	}
+}
+
+func createEmptyFile(p string) {
+	check(os.WriteFile(p, []byte(""), 0700))
+}
+
+func Dir() {
+	dirPath := "/tmp/gobyex-tempdir"
+	err := os.Mkdir(dirPath, 0700)
+	check(err)
+	defer os.RemoveAll(dirPath)
+
+	createEmptyFile(filepath.Join(dirPath, "file1"))
+
+	check(os.MkdirAll(filepath.Join(dirPath, "child", "grandchild"), 0700))
+
+	createEmptyFile(filepath.Join(dirPath, "child", "grandchild", "file1"))
+	createEmptyFile(filepath.Join(dirPath, "child", "grandchild", "file2"))
+	createEmptyFile(filepath.Join(dirPath, "child", "grandchild", "file3"))
+
+	check(os.Mkdir(filepath.Join(dirPath, "child", "grandchild", "dir1"), 0700))
+
+	entries, err := os.ReadDir(filepath.Join(dirPath, "child", "grandchild"))
+	check(err)
+
+	fmt.Println("Lisitng", filepath.Join(dirPath, "child", "grandchild"))
+	for _, entry := range entries {
+		fmt.Printf("%s, is dir? %t\n", entry.Name(), entry.IsDir())
+	}
+
+	check(os.Chdir(dirPath))
+
+	entries, err = os.ReadDir(".")
+	check(err)
+
+	fmt.Println("Listing", dirPath)
+	for _, entry := range entries {
+		fmt.Printf("%s, is dir? %t\n", entry.Name(), entry.IsDir())
+	}
+
+	fmt.Println("Walking the file tree at", dirPath)
+	// WalkDir is more efficient than Walk
+	check(filepath.WalkDir(".", walk))
+}
+
+func walk(p string, d fs.DirEntry, err error) error {
+	if err != nil {
+		return err
+	}
+
+	fmt.Println("  ", p, "is dir?", d.IsDir())
+	return nil
+}

exit/exit.go

@@ -0,0 +1,12 @@
+package exit
+
+import (
+	"fmt"
+	"os"
+)
+
+func Exit() {
+	defer fmt.Println("this will never get printed when using os.Exit()")
+
+	os.Exit(3)
+}

filepath/filepath.go

@@ -0,0 +1,26 @@
+package filepath
+
+import (
+	"fmt"
+	"path/filepath"
+	"strings"
+)
+
+func Filepath() {
+	p := filepath.Join("a", "b", "c", "d")
+	fmt.Println(p)
+
+	ext := filepath.Ext("main.go")
+	fmt.Printf("Extension is %s\n", ext)
+	fmt.Printf("Filename without ext is %s\n", strings.TrimSuffix("main.go", ext))
+
+	fmt.Printf("Base name is %s\n", filepath.Base("/a/b/c/file.go"))
+	fmt.Printf("Dirname is %s\n", filepath.Dir("/a/b/c/file.go"))
+
+	relPath, _ := filepath.Rel("/a/b", "/a/c/d/f")
+	fmt.Println("Rel path is", relPath)
+
+	fmt.Println("Is local?", filepath.IsLocal("filepath.go"))
+	fmt.Println("Is abs?", filepath.IsAbs("/a/b/c/d"))
+	fmt.Println("Is abs?", filepath.IsAbs("/a/b/c/d/.."))
+}

files/files.go

@@ -0,0 +1,83 @@
+package files
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"os"
+)
+
+func Files() {
+	Reading()
+	Writing()
+}
+
+func check(err error) {
+	if err != nil {
+		panic(err)
+	}
+}
+
+func Reading() {
+	data, err := os.ReadFile("/etc/hosts")
+	check(err)
+
+	fmt.Println("Contents:")
+	fmt.Println(string(data))
+
+	f, err := os.Open("/etc/hosts")
+	defer f.Close()
+	check(err)
+
+	bytes1 := make([]byte, 5)
+	n1, err := f.Read(bytes1)
+	check(err)
+
+	fmt.Printf("Read %d bytes: %v\n", n1, string(bytes1[:n1]))
+
+	o1, err := f.Seek(5, 0)
+	check(err)
+	bytes2 := make([]byte, 4)
+	n2, err := f.Read(bytes2)
+	check(err)
+	fmt.Printf("Read %d bytes @ %d: %v\n", n2, o1, string(bytes2[:n2]))
+
+	o2, err := f.Seek(5, 0)
+	check(err)
+	bytes3 := make([]byte, 4)
+	n3, err := io.ReadAtLeast(f, bytes3, 2)
+	check(err)
+	fmt.Printf("Read %d bytes @ %d: %v\n", n3, o2, string(bytes3))
+
+	o3, err := f.Seek(5, 0)
+	check(err)
+	br := bufio.NewReader(f)
+	bytes4, err := br.Peek(4)
+	check(err)
+	fmt.Printf("Read @ %d: %v\n", o3, string(bytes4))
+}
+
+func Writing() {
+	err := os.WriteFile("/tmp/go.files.write.txt", []byte("hello go!"), 0600)
+	check(err)
+
+	f, err := os.Create("/tmp/go.files.write2.txt")
+	check(err)
+
+	n1, err := f.Write([]byte{87, 73, 78})
+	check(err)
+	fmt.Printf("Wrote %d bytes\n", n1)
+
+	n2, err := f.WriteString(" macOS")
+	check(err)
+	fmt.Printf("Wrote %d bytes\n", n2)
+
+	f.Sync()
+
+	bw := bufio.NewWriter(f)
+	n3, err := bw.WriteString(" linux")
+	check(err)
+	fmt.Printf("Wrote %d bytes\n", n3)
+
+	bw.Flush()
+}

linefilter/linefilter.go

@@ -0,0 +1,21 @@
+package linefilter
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"strings"
+)
+
+func LineFilter() {
+	sc := bufio.NewScanner(os.Stdin)
+
+	for sc.Scan() {
+		cap := strings.ToUpper(sc.Text())
+		fmt.Println(cap)
+	}
+
+	if err := sc.Err(); err != nil {
+		panic(err)
+	}
+}

main.go

@@ -33,7 +33,12 @@ package main
 // import "git.sangeeth.dev/gobyexample/numberparsing"
 // import "git.sangeeth.dev/gobyexample/url"
 // import "git.sangeeth.dev/gobyexample/sha"
-import "git.sangeeth.dev/gobyexample/base64"
+// import "git.sangeeth.dev/gobyexample/base64"
+// import "git.sangeeth.dev/gobyexample/files"
+// import "git.sangeeth.dev/gobyexample/linefilter"
+// import "git.sangeeth.dev/gobyexample/exit"
+// import "git.sangeeth.dev/gobyexample/filepath"
+import "git.sangeeth.dev/gobyexample/dir"
 
 func main() {
 	// runes.Runes()
@@ -69,5 +74,10 @@ func main() {
 	// numberparsing.NumberParsing()
 	// url.Url()
 	// sha.Sha()
-	base64.Base64()
+	// base64.Base64()
+	// files.Files()
+	// linefilter.LineFilter()
+	// exit.Exit()
+	// filepath.Filepath()
+	dir.Dir()
 }