Replace deprecation ioutil fucntions (prometheus#456)

Go 1.16 deprecated several `io/ioutil` functions.
* `ioutil.ReadFile` -> `os.ReadFile`
* `ioutil.ReadAll` -> `io.ReadAll`
* `ioutil.ReadDir` -> `os.ReadDir`

Signed-off-by: SuperQ <superq@gmail.com>

Author: SuperQ

CONTRIBUTING.md

@@ -97,7 +97,7 @@ Many of the files are changing continuously and the data being read can in some
 reads in the same file.  Also, most of the files are relatively small (less than a few KBs), and system calls
 to the `stat` function will often return the wrong size.  Therefore, for most files it's recommended to read the 
 full file in a single operation using an internal utility function called `util.ReadFileNoStat`.
-This function is similar to `ioutil.ReadFile`, but it avoids the system call to `stat` to get the current size of
+This function is similar to `os.ReadFile`, but it avoids the system call to `stat` to get the current size of
 the file.
 
 Note that parsing the file's contents can still be performed one line at a time.  This is done by first reading 
@@ -113,7 +113,7 @@ the full file, and then using a scanner on the `[]byte` or `string` containing t
 ```
 
 The `/sys` filesystem contains many very small files which contain only a single numeric or text value.  These files
-can be read using an internal function called `util.SysReadFile` which is similar to `ioutil.ReadFile` but does
+can be read using an internal function called `util.SysReadFile` which is similar to `os.ReadFile` but does
 not bother to check the size of the file before reading.
 ```
     data, err := util.SysReadFile("/sys/class/power_supply/BAT0/capacity")

arp.go

@@ -15,8 +15,8 @@ package procfs
 
 import (
 	"fmt"
-	"io/ioutil"
 	"net"
+	"os"
 	"strconv"
 	"strings"
 )
@@ -53,7 +53,7 @@ type ARPEntry struct {
 // GatherARPEntries retrieves all the ARP entries, parse the relevant columns,
 // and then return a slice of ARPEntry's.
 func (fs FS) GatherARPEntries() ([]ARPEntry, error) {
-	data, err := ioutil.ReadFile(fs.proc.Path("net/arp"))
+	data, err := os.ReadFile(fs.proc.Path("net/arp"))
 	if err != nil {
 		return nil, fmt.Errorf("error reading arp %q: %w", fs.proc.Path("net/arp"), err)
 	}

bcache/get.go

@@ -16,7 +16,6 @@ package bcache
 import (
 	"bufio"
 	"fmt"
-	"io/ioutil"
 	"os"
 	"path"
 	"path/filepath"
@@ -204,7 +203,7 @@ func (p *parser) readValue(fileName string) uint64 {
 		return 0
 	}
 	path := path.Join(p.currentDir, fileName)
-	byt, err := ioutil.ReadFile(path)
+	byt, err := os.ReadFile(path)
 	if err != nil {
 		if !os.IsNotExist(err) {
 			p.err = fmt.Errorf("failed to read: %s", path)

blockdevice/stats.go

@@ -17,7 +17,6 @@ import (
 	"bufio"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"os"
 	"strings"
 
@@ -293,7 +292,7 @@ func (fs FS) ProcDiskstats() ([]Diskstats, error) {
 
 // SysBlockDevices lists the device names from /sys/block/<dev>.
 func (fs FS) SysBlockDevices() ([]string, error) {
-	deviceDirs, err := ioutil.ReadDir(fs.sys.Path(sysBlockPath))
+	deviceDirs, err := os.ReadDir(fs.sys.Path(sysBlockPath))
 	if err != nil {
 		return nil, err
 	}
@@ -309,7 +308,7 @@ func (fs FS) SysBlockDevices() ([]string, error) {
 // and 11 if they are not available.
 func (fs FS) SysBlockDeviceStat(device string) (IOStats, int, error) {
 	stat := IOStats{}
-	bytes, err := ioutil.ReadFile(fs.sys.Path(sysBlockPath, device, "stat"))
+	bytes, err := os.ReadFile(fs.sys.Path(sysBlockPath, device, "stat"))
 	if err != nil {
 		return stat, 0, err
 	}

btrfs/get.go

@@ -14,7 +14,6 @@
 package btrfs
 
 import (
-	"io/ioutil"
 	"os"
 	"path"
 	"path/filepath"
@@ -122,7 +121,7 @@ func (r *reader) readValue(n string) (v uint64) {
 
 // listFiles returns a list of files for a directory of the reader.
 func (r *reader) listFiles(p string) []string {
-	files, err := ioutil.ReadDir(path.Join(r.path, p))
+	files, err := os.ReadDir(path.Join(r.path, p))
 	if err != nil {
 		r.err = err
 		return nil
@@ -164,7 +163,7 @@ func (r *reader) readAllocationStats(d string) (a *AllocationStats) {
 
 // readLayouts reads all Btrfs layout statistics for the current path.
 func (r *reader) readLayouts() map[string]*LayoutUsage {
-	files, err := ioutil.ReadDir(r.path)
+	files, err := os.ReadDir(r.path)
 	if err != nil {
 		r.err = err
 		return nil

internal/util/parse.go

@@ -14,7 +14,7 @@
 package util
 
 import (
-	"io/ioutil"
+	"os"
 	"strconv"
 	"strings"
 )
@@ -66,7 +66,7 @@ func ParsePInt64s(ss []string) ([]*int64, error) {
 
 // ReadUintFromFile reads a file and attempts to parse a uint64 from it.
 func ReadUintFromFile(path string) (uint64, error) {
-	data, err := ioutil.ReadFile(path)
+	data, err := os.ReadFile(path)
 	if err != nil {
 		return 0, err
 	}
@@ -75,7 +75,7 @@ func ReadUintFromFile(path string) (uint64, error) {
 
 // ReadIntFromFile reads a file and attempts to parse a int64 from it.
 func ReadIntFromFile(path string) (int64, error) {
-	data, err := ioutil.ReadFile(path)
+	data, err := os.ReadFile(path)
 	if err != nil {
 		return 0, err
 	}

internal/util/readfile.go

@@ -15,12 +15,11 @@ package util
 
 import (
 	"io"
-	"io/ioutil"
 	"os"
 )
 
-// ReadFileNoStat uses ioutil.ReadAll to read contents of entire file.
-// This is similar to ioutil.ReadFile but without the call to os.Stat, because
+// ReadFileNoStat uses io.ReadAll to read contents of entire file.
+// This is similar to os.ReadFile but without the call to os.Stat, because
 // many files in /proc and /sys report incorrect file sizes (either 0 or 4096).
 // Reads a max file size of 512kB.  For files larger than this, a scanner
 // should be used.
@@ -34,5 +33,5 @@ func ReadFileNoStat(filename string) ([]byte, error) {
 	defer f.Close()
 
 	reader := io.LimitReader(f, maxBufferSize)
-	return ioutil.ReadAll(reader)
+	return io.ReadAll(reader)
 }

internal/util/sysreadfile.go

@@ -22,7 +22,7 @@ import (
 	"syscall"
 )
 
-// SysReadFile is a simplified ioutil.ReadFile that invokes syscall.Read directly.
+// SysReadFile is a simplified os.ReadFile that invokes syscall.Read directly.
 // https://github.com/prometheus/node_exporter/pull/728/files
 //
 // Note that this function will not read files larger than 128 bytes.
@@ -34,7 +34,7 @@ func SysReadFile(file string) (string, error) {
 	defer f.Close()
 
 	// On some machines, hwmon drivers are broken and return EAGAIN.  This causes
-	// Go's ioutil.ReadFile implementation to poll forever.
+	// Go's os.ReadFile implementation to poll forever.
 	//
 	// Since we either want to read data or bail immediately, do the simplest
 	// possible read using syscall directly.

ipvs.go

@@ -20,7 +20,6 @@ import (
 	"errors"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"net"
 	"os"
 	"strconv"
@@ -84,7 +83,7 @@ func parseIPVSStats(r io.Reader) (IPVSStats, error) {
 		stats       IPVSStats
 	)
 
-	statContent, err := ioutil.ReadAll(r)
+	statContent, err := io.ReadAll(r)
 	if err != nil {
 		return IPVSStats{}, err
 	}

iscsi/get.go

@@ -17,7 +17,6 @@ package iscsi
 import (
 	"errors"
 	"fmt"
-	"io/ioutil"
 	"os"
 	"path/filepath"
 	"strconv"
@@ -60,7 +59,7 @@ func GetStats(iqnPath string) (*Stats, error) {
 
 // isPathEnable checks if the file "enable" contain enable message.
 func isPathEnable(path string) (bool, error) {
-	enableReadout, err := ioutil.ReadFile(filepath.Join(path, "enable"))
+	enableReadout, err := os.ReadFile(filepath.Join(path, "enable"))
 	if err != nil {
 		return false, fmt.Errorf("iscsi: isPathEnable ReadFile error %w", err)
 	}
@@ -74,7 +73,7 @@ func isPathEnable(path string) (bool, error) {
 func getLunLinkTarget(lunPath string) (lunObject LUN, err error) {
 	lunObject.Name = filepath.Base(lunPath)
 	lunObject.LunPath = lunPath
-	files, err := ioutil.ReadDir(lunPath)
+	files, err := os.ReadDir(lunPath)
 	if err != nil {
 		return lunObject, fmt.Errorf("getLunLinkTarget: ReadDir path %q: %w", lunPath, err)
 	}
@@ -144,7 +143,7 @@ func (fs FS) GetFileioUdev(fileioNumber string, objectName string) (*FILEIO, err
 	if _, err := os.Stat(udevPath); os.IsNotExist(err) {
 		return nil, fmt.Errorf("iscsi: GetFileioUdev: fileio_%s is missing file name", fileio.Fnumber)
 	}
-	filename, err := ioutil.ReadFile(udevPath)
+	filename, err := os.ReadFile(udevPath)
 	if err != nil {
 		return nil, fmt.Errorf("iscsi: GetFileioUdev: Cannot read filename from udev link %q", udevPath)
 	}
@@ -166,7 +165,7 @@ func (fs FS) GetIblockUdev(iblockNumber string, objectName string) (*IBLOCK, err
 	if _, err := os.Stat(udevPath); os.IsNotExist(err) {
 		return nil, fmt.Errorf("iscsi: GetIBlockUdev: iblock_%s is missing file name", iblock.Bnumber)
 	}
-	filename, err := ioutil.ReadFile(udevPath)
+	filename, err := os.ReadFile(udevPath)
 	if err != nil {
 		return nil, fmt.Errorf("iscsi: GetIBlockUdev: Cannot read iblock from udev link %q", udevPath)
 	}
@@ -193,7 +192,7 @@ func (fs FS) GetRBDMatch(rbdNumber string, poolImage string) (*RBD, error) {
 		if _, err := os.Stat(systemPoolPath); os.IsNotExist(err) {
 			continue
 		}
-		bSystemPool, err := ioutil.ReadFile(systemPoolPath)
+		bSystemPool, err := os.ReadFile(systemPoolPath)
 		if err != nil {
 			continue
 		} else {
@@ -204,7 +203,7 @@ func (fs FS) GetRBDMatch(rbdNumber string, poolImage string) (*RBD, error) {
 		if _, err := os.Stat(systemImagePath); os.IsNotExist(err) {
 			continue
 		}
-		bSystemImage, err := ioutil.ReadFile(systemImagePath)
+		bSystemImage, err := os.ReadFile(systemImagePath)
 		if err != nil {
 			continue
 		} else {