Change https://golang.org/cl/53412 mentions this issue: os/file: trim the last slash of $TMPDIR``

hello @davecheney
The shell knows nothing... Just blank output.

But if fmt.Println(os.TempDir()), OS X will tell you /var/folders/t9/uaiyebqwpojxbaywgebzmx/T/, while the Unix told you /tmp.

If you just want to get the temp directory, that's fine, but once you want to get the file name you created in the temp directory, and trim the temp dir, it will be different.

https://play.golang.org/p/yz4DLEPoNr

package main

import (
	"fmt"
	"io/ioutil"
	"os"
	"strings"
)

func main() {
	file, _ := ioutil.TempFile(os.TempDir(), "file-")
	fp := strings.TrimPrefix(file.Name(), os.TempDir())
	fmt.Println(file.Name())
	fmt.Println(fp)
}

In the Unix systems, you'll get:

/tmp/file-054003078
/file-054003078

But in OS X:

/var/folders/t9/uaiyebqwpojxbaywgebzmx/T/file-054003078
file-054003078

I got a same A, but a different B.

For serving a file:
If the temp file name is /temp-file-in-temp-dir, and the server's path is /var/www/files, I can combine it with df := fmt.Sprintf("%s%s",path,filename) in Unix, but in OS X, it will be df := fmt.Sprintf("%s/%s",path,filename) since the filename doesn't contains the first slash.

It's not good that a same program behave inconsistently on different systems.

While I would also recommend filepath.Join, use always "%s/%s" with printf. UNIX treats "a//b" as "a/b" and therefore "%s/%s" works regardless whether the first path is terminated by a slash or not.

Even if we would define that TempDir should always return a cleaned path as produced by filepath.Clean you couldn't assume that it never ends in a slash, because it could return the root path "/".

That's a little embarrassed.... I've even created a code-review request in Gerrit....

BTW, is there any standard for return a directory's name?

Thanks you guys.

I think that is the definition that is relevant:

http://pubs.opengroup.org/onlinepubs/009695399/basedefs/xbd_chap03.html#tag_03_266

A pathname may optionally contain one or more trailing slashes. All what TempDir is doing is returning a pathname.

Got that, thank you very much! @ulikunitz @davecheney