refactor: move from io/ioutil to io and os packages

The io/ioutil package has been deprecated as of Go 1.16, see
https://golang.org/doc/go1.16#ioutil. This commit replaces the existing
io/ioutil functions with their new definitions in io and os packages.

This commit also uses
`testing#T.TempDir` (https://pkg.go.dev/testing#T.TempDir) to create
temporary directory in tests instead of `ioutil.TempDir`.

Signed-off-by: Eng Zer Jun <[email protected]>

cmds/boot/fbnetboot/main.go

@@ -10,7 +10,7 @@ import (
 	"errors"
 	"flag"
 	"fmt"
-	"io/ioutil"
+	"io"
 	"log"
 	"net"
 	"net/http"
@@ -253,7 +253,7 @@ func boot(ifname string, dhcp dhcpFunc) error {
 	if resp.StatusCode != 200 {
 		return fmt.Errorf("status code is not 200 OK: %d", resp.StatusCode)
 	}
-	body, err := ioutil.ReadAll(resp.Body)
+	body, err := io.ReadAll(resp.Body)
 	if err != nil {
 		return fmt.Errorf("DHCP: cannot read boot file from the network: %v", err)
 	}
@@ -270,7 +270,7 @@ func boot(ifname string, dhcp dhcpFunc) error {
 	if filename == "." || filename == "" {
 		return fmt.Errorf("invalid empty file name extracted from file path %s", u.Path)
 	}
-	if err = ioutil.WriteFile(filename, body, 0o400); err != nil {
+	if err = os.WriteFile(filename, body, 0o400); err != nil {
 		return fmt.Errorf("DHCP: cannot write to file %s: %v", filename, err)
 	}
 	debug("DHCP: saved boot file to %s", filename)
@@ -315,7 +315,7 @@ func loadCaCerts() (*x509.CertPool, error) {
 		debug("certs: rootCAs == nil")
 		rootCAs = x509.NewCertPool()
 	}
-	caCerts, err := ioutil.ReadFile(*caCertFile)
+	caCerts, err := os.ReadFile(*caCertFile)
 	if err != nil {
 		return nil, fmt.Errorf("could not find cert file '%v' - %v", *caCertFile, err)
 	}

cmds/boot/localboot/grub.go

@@ -6,7 +6,6 @@ package main
 
 import (
 	"encoding/hex"
-	"io/ioutil"
 	"log"
 	"os"
 	"path"
@@ -230,7 +229,7 @@ func ScanGrubConfigs(devices block.BlockDevices, basedir string) []jsonboot.Boot
 			return nil
 		}
 		log.Printf("Parsing %s", currentPath)
-		data, err := ioutil.ReadFile(currentPath)
+		data, err := os.ReadFile(currentPath)
 		if err != nil {
 			return err
 		}

cmds/contrib/flash/flash.go

@@ -38,7 +38,6 @@ import (
 	"errors"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"log"
 	"os"
 	"sort"
@@ -160,7 +159,7 @@ func run(args []string, supportedProgrammers map[string]programmerInit) (reterr
 		if _, err := io.ReadFull(f, buf); err != nil {
 			return err
 		}
-		if leftover, err := io.Copy(ioutil.Discard, f); err != nil {
+		if leftover, err := io.Copy(io.Discard, f); err != nil {
 			return err
 		} else if leftover != 0 {
 			return fmt.Errorf("flash size (%#x) unequal to file size (%#x)", len(buf), int64(len(buf))+leftover)

cmds/contrib/spidev/spidev.go

@@ -21,7 +21,6 @@ package main
 import (
 	"errors"
 	"io"
-	"io/ioutil"
 	"log"
 	"os"
 
@@ -71,7 +70,7 @@ func run(args []string, spiOpen spiOpenFunc, input io.Reader, output io.Writer)
 	switch fs.Args()[0] {
 	case "raw":
 		// Create transfer from stdin.
-		tx, err := ioutil.ReadAll(input)
+		tx, err := io.ReadAll(input)
 		if err != nil {
 			return err
 		}

cmds/core/cat/cat_test.go

@@ -9,7 +9,6 @@ package main
 import (
 	"bytes"
 	"fmt"
-	"io/ioutil"
 	"os"
 	"path/filepath"
 	"reflect"
@@ -19,14 +18,11 @@ import (
 // setup writes a set of files, putting 1 byte in each file.
 func setup(t *testing.T, data []byte) (string, error) {
 	t.Logf(":: Creating simulation data. ")
-	dir, err := ioutil.TempDir("", "cat.dir")
-	if err != nil {
-		return "", err
-	}
+	dir := t.TempDir()
 
 	for i, d := range data {
 		n := fmt.Sprintf("%v%d", filepath.Join(dir, "file"), i)
-		if err := ioutil.WriteFile(n, []byte{d}, 0o666); err != nil {
+		if err := os.WriteFile(n, []byte{d}, 0o666); err != nil {
 			return "", err
 		}
 	}
@@ -45,7 +41,6 @@ func TestCat(t *testing.T) {
 	if err != nil {
 		t.Fatalf("setup has failed, %v", err)
 	}
-	defer os.RemoveAll(dir)
 
 	for i := range someData {
 		files = append(files, fmt.Sprintf("%v%d", filepath.Join(dir, "file"), i))

cmds/core/chmod/chmod_test.go

@@ -6,7 +6,6 @@ package main
 
 import (
 	"bytes"
-	"io/ioutil"
 	"os"
 	"os/exec"
 	"path/filepath"
@@ -29,13 +28,7 @@ func run(c *exec.Cmd) (string, string, error) {
 
 func TestChmodSimple(t *testing.T) {
 	// Temporary directories.
-	tempDir, err := ioutil.TempDir("", "TestChmodSimple")
-	if err != nil {
-		t.Fatalf("cannot create temporary directory: %v", err)
-	}
-	defer os.RemoveAll(tempDir)
-
-	f, err := ioutil.TempFile(tempDir, "BLAH1")
+	f, err := os.CreateTemp(t.TempDir(), "BLAH1")
 	if err != nil {
 		t.Fatalf("cannot create temporary file: %v", err)
 	}
@@ -100,11 +93,7 @@ func checkPath(t *testing.T, path string, instruction string, v fileModeTrans) {
 
 func TestChmodRecursive(t *testing.T) {
 	// Temporary directories.
-	tempDir, err := ioutil.TempDir("", "TestChmodRecursive")
-	if err != nil {
-		t.Fatalf("cannot create temporary directory: %v", err)
-	}
-	defer os.RemoveAll(tempDir)
+	tempDir := t.TempDir()
 
 	var targetDirectories []string
 	for _, dir := range []string{
@@ -148,8 +137,7 @@ func TestChmodRecursive(t *testing.T) {
 
 		// Set permissions using chmod.
 		c := testutil.Command(t, "-R", k, tempDir)
-		err = c.Run()
-		if err != nil {
+		if err := c.Run(); err != nil {
 			t.Fatalf("setting permissions failed: %v", err)
 		}
 
@@ -162,19 +150,15 @@ func TestChmodRecursive(t *testing.T) {
 
 func TestChmodReference(t *testing.T) {
 	// Temporary directories.
-	tempDir, err := ioutil.TempDir("", "TestChmodReference")
-	if err != nil {
-		t.Fatalf("cannot create temporary directory: %v", err)
-	}
-	defer os.RemoveAll(tempDir)
+	tempDir := t.TempDir()
 
-	sourceFile, err := ioutil.TempFile(tempDir, "BLAH1")
+	sourceFile, err := os.CreateTemp(tempDir, "BLAH1")
 	if err != nil {
 		t.Fatalf("cannot create temporary file: %v", err)
 	}
 	defer sourceFile.Close()
 
-	targetFile, err := ioutil.TempFile(tempDir, "BLAH2")
+	targetFile, err := os.CreateTemp(tempDir, "BLAH2")
 	if err != nil {
 		t.Fatalf("cannot create temporary file: %v", err)
 	}
@@ -209,13 +193,7 @@ func TestChmodReference(t *testing.T) {
 }
 
 func TestInvocationErrors(t *testing.T) {
-	tempDir, err := ioutil.TempDir("", "TestInvocationErrors")
-	if err != nil {
-		t.Fatalf("cannot create temporary directory: %v", err)
-	}
-	defer os.RemoveAll(tempDir)
-
-	f, err := ioutil.TempFile(tempDir, "BLAH1")
+	f, err := os.CreateTemp(t.TempDir(), "BLAH1")
 	if err != nil {
 		t.Fatalf("cannot create temporary file: %v", err)
 	}

cmds/core/comm/comm_test.go

@@ -6,7 +6,6 @@ package main
 
 import (
 	"fmt"
-	"io/ioutil"
 	"os"
 	"path/filepath"
 	"testing"
@@ -55,18 +54,14 @@ var commTests = []struct {
 
 // TestComm implements a table-drivent test.
 func TestComm(t *testing.T) {
-	tmpDir, err := ioutil.TempDir("", "comm")
-	if err != nil {
-		t.Fatal(err)
-	}
-	defer os.RemoveAll(tmpDir)
+	tmpDir := t.TempDir()
 
 	for _, test := range commTests {
 		// Write inputs into the two files
 		var files [2]string
 		for i, contents := range []string{test.in1, test.in2} {
 			files[i] = filepath.Join(tmpDir, fmt.Sprintf("txt%d", i))
-			if err := ioutil.WriteFile(files[i], []byte(contents), 0o600); err != nil {
+			if err := os.WriteFile(files[i], []byte(contents), 0o600); err != nil {
 				t.Fatalf("Failed to create test file %d: %v", i, err)
 			}
 		}

cmds/core/cp/cp_test.go

@@ -9,7 +9,6 @@ package main
 import (
 	"bytes"
 	"fmt"
-	"io/ioutil"
 	"log"
 	"math/rand"
 	"os"
@@ -38,7 +37,7 @@ func resetFlags() {
 
 // randomFile create a random file with random content
 func randomFile(fpath, prefix string) (*os.File, error) {
-	f, err := ioutil.TempFile(fpath, prefix)
+	f, err := os.CreateTemp(fpath, prefix)
 	if err != nil {
 		return nil, err
 	}
@@ -56,7 +55,7 @@ func randomFile(fpath, prefix string) (*os.File, error) {
 func createFilesTree(root string, maxDepth, depth int) error {
 	// create more one dir if don't achieve the maxDepth
 	if depth < maxDepth {
-		newDir, err := ioutil.TempDir(root, fmt.Sprintf("cpdir_%d_", depth))
+		newDir, err := os.MkdirTemp(root, fmt.Sprintf("cpdir_%d_", depth))
 		if err != nil {
 			return err
 		}
@@ -80,11 +79,7 @@ func createFilesTree(root string, maxDepth, depth int) error {
 // TestCpsSimple make a simple test for copy file-to-file
 // cmd-line equivalent: cp file file-copy
 func TestCpSimple(t *testing.T) {
-	tempDir, err := ioutil.TempDir("", "TestCpSimple")
-	if err != nil {
-		t.Fatal(err)
-	}
-	defer os.RemoveAll(tempDir)
+	tempDir := t.TempDir()
 
 	f, err := randomFile(tempDir, "src-")
 	if err != nil {
@@ -109,17 +104,8 @@ func TestCpSrcDirectory(t *testing.T) {
 	flags.recursive = false
 	defer resetFlags()
 
-	tempDir, err := ioutil.TempDir("", "TestCpSrcDirectory")
-	if err != nil {
-		t.Fatal(err)
-	}
-	defer os.RemoveAll(tempDir)
-
-	tempDirTwo, err := ioutil.TempDir("", "TestCpSrcDirectoryTwo")
-	if err != nil {
-		t.Fatal(err)
-	}
-	defer os.RemoveAll(tempDirTwo)
+	tempDir := t.TempDir()
+	tempDirTwo := t.TempDir()
 
 	// capture log output to verify
 	var logBytes bytes.Buffer
@@ -144,11 +130,7 @@ func TestCpRecursive(t *testing.T) {
 	flags.recursive = true
 	defer resetFlags()
 
-	tempDir, err := ioutil.TempDir("", "TestCpRecursive")
-	if err != nil {
-		t.Fatal(err)
-	}
-	defer os.RemoveAll(tempDir)
+	tempDir := t.TempDir()
 
 	srcDir := filepath.Join(tempDir, "src")
 	if err := os.Mkdir(srcDir, 0o755); err != nil {
@@ -159,7 +141,7 @@ func TestCpRecursive(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	if err = createFilesTree(srcDir, maxDirDepth, 0); err != nil {
+	if err := createFilesTree(srcDir, maxDirDepth, 0); err != nil {
 		t.Fatalf("cannot create files tree on directory %q: %v", srcDir, err)
 	}
 
@@ -198,11 +180,7 @@ func TestCpRecursive(t *testing.T) {
 func TestCpRecursiveMultiple(t *testing.T) {
 	flags.recursive = true
 	defer resetFlags()
-	tempDir, err := ioutil.TempDir("", "TestCpRecursiveMultiple")
-	if err != nil {
-		t.Fatal(err)
-	}
-	defer os.RemoveAll(tempDir)
+	tempDir := t.TempDir()
 
 	dstTest := filepath.Join(tempDir, "destination")
 	if err := os.Mkdir(dstTest, 0o755); err != nil {
@@ -212,11 +190,9 @@ func TestCpRecursiveMultiple(t *testing.T) {
 	// create multiple random directories sources
 	srcDirs := []string{}
 	for i := 0; i < maxDirDepth; i++ {
-		srcTest, err := ioutil.TempDir(tempDir, "src-")
-		if err != nil {
-			t.Fatalf("Failed on build directory %v: %v\n", srcTest, err)
-		}
-		if err = createFilesTree(srcTest, maxDirDepth, 0); err != nil {
+		srcTest := t.TempDir()
+
+		if err := createFilesTree(srcTest, maxDirDepth, 0); err != nil {
 			t.Fatalf("cannot create files tree on directory %v: %v", srcTest, err)
 		}
 
@@ -247,11 +223,7 @@ func TestCpRecursiveMultiple(t *testing.T) {
 // using -P don't follow symlinks, create other symlink
 // cmd-line equivalent: $ cp -P symlink symlink-copy
 func TestCpSymlink(t *testing.T) {
-	tempDir, err := ioutil.TempDir("", "TestCpSymlink")
-	if err != nil {
-		t.Fatal(err)
-	}
-	defer os.RemoveAll(tempDir)
+	tempDir := t.TempDir()
 
 	f, err := randomFile(tempDir, "src-")
 	if err != nil {