When should I use a trailing slash on a directory?

Question

Possible Duplicate:
How linux handles multiple path separators (/home////username///file)

Most commands I use in linux behave exactly the same whether I include the trailing slash / character on the end of a directory name or not.

For example:

ls /home/cklein
ls /home/cklein/

cp foo bar
cp foo/ bar/

When does this trailing slash matter? What is the semantic meaning of the trailing slash?

Answer 1

One good example is moving a file into a directory:

mv some_file foo

vs.

mv some_file foo/

If foo doesn't exist, the first will rename some_file to foo, rather than the intended foo/some_file; the second will complain, which is what you want.

If foo does exists but isn't a directory, the first can clobber the foo file; again, the second will complain.

cp presents similar issues.

Working on some old versions of SunOS, I developed the habit of appending /., because the system actually ignored a trailing / on a file name; for example, /etc/motd/ would refer to the file rather than being an error. Later versions of SunOS / Solaris don't seem to have that problem.

Answer 2

It is completely dependent on the tool. rm won't let you remove a symlink to a directory if there's a slash at the end, and rsync does different things if the source file specification has a slash at the end.

Answer 3

foo/ is like foo/., so if foo is a symlink to a directory, foo/ is a directory (not a symlink), and if foo is not a directory or a symlink to a directory, then you get a ENOTDIR error for anything trying to access foo/. That's the behavior on Linux.

Behavior may differ on other systems.

See here and here and here to see what POSIX/SUS have to say about it.

Answer 4

In rsync, the man page reads as follows:

   A trailing slash on the source changes this behavior to avoid  creating
   an  additional  directory level at the destination.  You can think of a
   trailing / on a source as meaning "copy the contents of this directory"
   as  opposed  to  "copy  the  directory  by name", but in both cases the
   attributes of the containing directory are transferred to the  contain-
   ing  directory on the destination.  In other words, each of the follow-
   ing commands copies the files in the same way, including their  setting
   of the attributes of /dest/foo:

          rsync -av /src/foo /dest
          rsync -av /src/foo/ /dest/foo

The trailing slash on the destination doesn't matter at all. Only on the source. (And then, of course, it only matters if the source is a directory rather than a single file or a glob.)

To illustrate the directory to directory use case:

$ mkdir foo bar baz
$ chmod 700 foo
$ chmod 750 bar
$ chmod 705 baz
$ echo hello > foo/file1
$ chmod 606 foo/file1 
$ ls -n
total 0
drwxr-x---  2 501  20   68 Aug  8 15:29 bar/
drwx---r-x  2 501  20   68 Aug  8 15:29 baz/
drwx------  3 501  20  102 Aug  8 15:30 foo/
$ ls -n foo
total 8
-rw----rw-  1 501  20  6 Aug  8 15:30 file1
$ rsync -a foo bar
$ rsync -a foo baz/
$ rsync -a foo bif
$ rsync -a foo bonk/
$ ls -n
total 0
drwxr-x---  3 501  20  102 Aug  8 15:30 bar/
drwx---r-x  3 501  20  102 Aug  8 15:30 baz/
drwxr-xr-x  3 501  20  102 Aug  8 15:30 bif/
drwxr-xr-x  3 501  20  102 Aug  8 15:30 bonk/
drwx------  3 501  20  102 Aug  8 15:30 foo/
$ ls -n *
bar:
total 0
drwx------  3 501  20  102 Aug  8 15:30 foo/

baz:
total 0
drwx------  3 501  20  102 Aug  8 15:30 foo/

bif:
total 0
drwx------  3 501  20  102 Aug  8 15:30 foo/

bonk:
total 0
drwx------  3 501  20  102 Aug  8 15:30 foo/

foo:
total 8
-rw----rw-  1 501  20  6 Aug  8 15:30 file1
$ rm -rf b*
$ mkdir bar baz
$ chmod 750 bar
$ chmod 705 baz
$ rsync -a foo/ bar
$ rsync -a foo/ baz/
$ rsync -a foo/ bif
$ rsync -a foo/ bonk/
$ ls -n
total 0
drwx------  3 501  20  102 Aug  8 15:30 bar/
drwx------  3 501  20  102 Aug  8 15:30 baz/
drwx------  3 501  20  102 Aug  8 15:30 bif/
drwx------  3 501  20  102 Aug  8 15:30 bonk/
drwx------  3 501  20  102 Aug  8 15:30 foo/
$ ls -n *
bar:
total 8
-rw----rw-  1 501  20  6 Aug  8 15:30 file1

baz:
total 8
-rw----rw-  1 501  20  6 Aug  8 15:30 file1

bif:
total 8
-rw----rw-  1 501  20  6 Aug  8 15:30 file1

bonk:
total 8
-rw----rw-  1 501  20  6 Aug  8 15:30 file1

foo:
total 8
-rw----rw-  1 501  20  6 Aug  8 15:30 file1
$