I've been writing some code to learn about the library changes in Go 1.16.
The following code uses filepath.Glob to get a slice of matching
filenames, then uses os.ReadDir to get more information about these
files. I found that os.ReadDir reports a file not found error for the
filenames returned by filepath.Glob. I do not understand why, as when I
use os.Lstat there are no errors. This code is extracted and simplified
from a longer program I wrote.
This code has been compiled w/ go1.16.1 and I'm getting the same error
messages.
I do not understand why. I would have expected that os.ReadDir can find
the filename just as os.Lstat does.
--rob solomon
// rddirpblm to isolate the problem w/ going from filepath.Glob to
os.ReadDir on Win10.
package main
import (
"fmt"
"os"
"path/filepath"
"runtime"
"strconv"
)
const LastAltered = "11 Mar 2021"
/*
Revision History
----------------
11 Mar 21 -- Isolating Glob -> ReadDir issue. Go 1.16 is deprecating
ioutil functions.
*/
func main() {
var err error
fmt.Print("rddirpblm LastAltered ", LastAltered, ", compiled using
", runtime.Version(), ".")
fmt.Println()
direntries := make([]os.DirEntry, 0, 500)
sepstring := string(filepath.Separator)
HomeDirStr, e := os.UserHomeDir() // HomeDir code used for
processing ~ symbol meaning home directory.
if e != nil {
fmt.Fprintln(os.Stderr, e)
HomeDirStr = ""
}
HomeDirStr = HomeDirStr + sepstring
fmt.Println(" HomeDirStr is", HomeDirStr)
globfor := "*.txt"
filenamesStringSlice, err := filepath.Glob(globfor)
if err != nil {
fmt.Fprintln(os.Stderr, err, " Exiting.")
os.Exit(1)
}
for i := 0; i < 20; i++ {
fn := filenamesStringSlice[i]
direntry, err := os.ReadDir(fn)
if err != nil {
fmt.Fprintln(os.Stderr, "fn =", fn, err)
fmt.Fprintln(os.Stderr, "Will try os.Lstat")
fi, er := os.Lstat(fn)
if er != nil {
fmt.Fprintln(os.Stderr, err)
}
fmt.Println("From os.Lstat: Name =", fi.Name(), ", Size =",
fi.Size(), ", IsDir =", fi.IsDir())
fmt.Println()
continue
}
if len(direntry) > 1 {
fmt.Fprintln(os.Stderr, " expecting only 1 direntry, but
len(direntry) is", len(direntry), ". Don't know what this means yet.")
}
direntries = append(direntries, direntry[0])
}
for _, d := range direntries {
f, err := d.Info()
if err != nil {
fmt.Fprintln(os.Stderr, err, ". No idea why this caused an
error.")
}
sizestr := strconv.FormatInt(f.Size(), 10)
if f.Size() > 100000 {
sizestr = AddCommas(sizestr)
}
fmt.Printf("%17s %s %s\n", sizestr, sizestr, d.Name())
} // end for range direntries
} // end main
//--------------------------------------------------------------------
InsertByteSlice
func InsertIntoByteSlice(slice, insertion []byte, index int) []byte {
return append(slice[:index], append(insertion, slice[index:]...)...)
} // InsertIntoByteSlice
//----------------------------------------------------------------------
AddCommas
func AddCommas(instr string) string {
//var Comma []byte = []byte{','} Getting error that type can be
omitted
Comma := []byte{','}
BS := make([]byte, 0, 15)
BS = append(BS, instr...)
i := len(BS)
for NumberOfCommas := i / 3; (NumberOfCommas > 0) && (i > 3);
NumberOfCommas-- {
i -= 3
BS = InsertIntoByteSlice(BS, Comma, i)
}
return string(BS)
} // AddCommas
// ------------------------------- MyReadDir
-----------------------------------
func MyReadDir(dir string) []os.DirEntry {
dirname, err := os.Open(dir)
if err != nil {
fmt.Fprintln(os.Stderr, err)
return nil
}
defer dirname.Close()
names, err := dirname.Readdirnames(0) // zero means read all names
into the returned []string
if err != nil {
fmt.Fprintln(os.Stderr, err)
return nil
}
direntries := make([]os.DirEntry, 0, len(names))
for _, name := range names {
d, err := os.ReadDir(name)
if err != nil {
fmt.Fprintln(os.Stderr, " Error from os.ReadDir. ", err)
continue
}
if len(d) > 1 {
fmt.Fprintln(os.Stderr, " expected len(d) == 1, but it's",
len(d), ", which I don't yet understand.")
}
direntries = append(direntries, d[0])
}
return direntries
} // MyReadDir
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