[go-nuts] Realpath?
Taru Karttunen
Has anyone written a realpath(3) replacement in Go?
- Taru Karttunen
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Michael Hoisie
Evan Shaw
> Check out the Clean function in http://golang.org/pkg/path/
symlinks into account. I think realpath could be added to the syscall
package easily enough.
- Evan
Taru Karttunen
> That's close, but not quite the same thing since it doesn't take
> symlinks into account. I think realpath could be added to the syscall
> package easily enough.
path.Clean misses that. realpath is implemented in libc without
any syscalls so using a syscall is not possibility.
Just wanting to avoid the hassle of reinventing and debugging
the wheel again.
- Taru Karttunen
Evan Shaw
> The symlink functionality is the most important part for me and
> path.Clean misses that. realpath is implemented in libc without
> any syscalls so using a syscall is not possibility.
someone's going to have to reinvent the wheel (or find a version with
a permissive license that can be adapted to Go).
- Evan
Koala Yeung
Made some more changes and put it on Github:
https://github.com/yookoala/realpath
Please tell me if there is anything needed to be changed.
Koala Yeung
Koala Yeung於 2012年7月16日星期一UTC+8下午3時48分39秒寫道：
Hello all,
Thanks Taru for the implementation. It seems the code fails with Go 1
I've changed it so it can work in Go 1 (Not sure if I got it right)
package realpath
import (
"os"
"fmt"
"bytes"
)
func Realpath(filepath string) (string, error) {
if len(filepath)==0 { return "", os.ErrInvalid }
sepStr := string(os.PathSeparator)
if filepath[0] != os.PathSeparator {
pwd, err := os.Getwd()
if err!=nil { return "", err }
filepath = pwd + sepStr + filepath
}
path := []byte(filepath)
nlinks := 0
start := 1
prev := 1
for start < len(path) {
c := nextComponent(path, start)
cur := c[start:]
switch {
case len(cur)==0:
copy(path[start:], path[start+1:])
path = path[0:len(path)-1]
case len(cur)==1 && cur[0]=='.':
if start+2 < len(path) { copy(path[start:], path[start+2:]) }
path = path[0:len(path)-2]
case len(cur)==2 && cur[0]=='.' && cur[1] == '.':
copy(path[prev:], path[start+2:])
path = path[0:len(path)+prev-(start+2)]
prev = 1
start = 1
default:
fi, err := os.Lstat(string(c))
if err!=nil { return "", err }
if fi.Mode() & os.ModeSymlink == os.ModeSymlink {
nlinks++
if nlinks > 16 { return "", os.ErrInvalid }
var dst string
dst, err = os.Readlink(string(c))
fmt.Printf("SYMLINK -> %s\n", dst)
rest := string(path[len(c):])
if dst[0] == '/' {
// Absolute links
path = []byte(dst + "/" + rest)
} else {
// Relative links
path = []byte(string(path[0:start])+dst+"/"+rest)
}
prev = 1
start = 1
} else {
// Directories
prev = start
start = len(c) + 1
}
}
}
for len(path)>1 && path[len(path)-1]=='/' { path = path[0:len(path)-1] }
return string(path), nil
}
func nextComponent(path []byte, start int) []byte {
v := bytes.IndexByte(path[start:], '/')
if v < 0 { return path }
return path[0 : start+v]
}
Please feel free to comment on the code
Thanks.
Koala Yeung
Taru Karttunen於 2010年4月23日星期五UTC+8上午2時55分51秒寫道：
Hello
Attached a preliminary implementation.
package realpath
import (
"fmt"
"os"
"bytes"
)
func RealPath(filepath string) (res string, err os.Error) {
if len(filepath)==0 { return "", os.EIO }
if filepath[0] != '/' {
pwd, err := os.Getwd()
if err!=nil { return }
filepath = pwd + "/" + filepath
}
path := []byte(filepath)
nlinks := 0
start := 1
prev := 1
for start < len(path) {
c := nextComponent(path, start)
cur := c[start:]
// fmt.Printf("Loop start %2d @ c '%s' - path %s\n", start, c, path)
// fmt.Printf("path[start:] = '%s'\n", path[start:])
// fmt.Printf("cur = '%s'\n", cur)
switch {
case len(cur)==0:
copy(path[start:], path[start+1:])
path = path[0:len(path)-1]
case len(cur)==1 && cur[0]=='.':
if start+2 < len(path) { copy(path[start:], path[start+2:]) }
path = path[0:len(path)-2]
case len(cur)==2 && cur[0]=='.' && cur[1] == '.':
copy(path[prev:], path[start+2:])
path = path[0:len(path)+prev-(start+2)]
prev = 1
start = 1
default:
fi, err := os.Lstat(string(c))
if err!=nil { return }
if fi.IsSymlink() {
nlinks++
if nlinks > 16 { return "", os.EIO }
var dst string
dst, err = os.Readlink(string(c))
fmt.Printf("SYMLINK -> %s\n", dst)
rest := string(path[len(c):])
if dst[0] == '/' {
// Absolute links
path = []byte(dst + "/" + rest)
} else {
// Relative links
path = []byte(string(path[0:start])+dst+"/"+rest)
}
prev = 1
start = 1
} else {
// Directories
prev = start
start = len(c) + 1
}
}
}
for len(path)>1 && path[len(path)-1]=='/' { path = path[0:len(path)-1] }
// fmt.Printf(" -> %s\n", path)
return string(path), nil
}
func nextComponent(path []byte, start int) []byte {
v := bytes.IndexByte(path[start:], '/')
if v < 0 { return path }
return path[0 : start+v]
}
Rémy Oudompheng
Rémy.
rgo...@redhat.com
On Monday, 16 July 2012 13:55:53 UTC+3, Rémy Oudompheng wrote:
Did you have a look at filepath.EvalSymlinks?
Rémy.
