Rsync is great for making sure that a destination directory is synchronised with a source directory. However, do you add a slash to the source and/or destination directory names, or do you not?

The answer is, it depends. Without a slash on the source directory means copy both the source directory, and the contents (recursively if specified) to the destination directory while adding a trailing slash means only copy the contents of the source directory, recursively if specified, to the destination. Easy?

If we take the following as the source directory:

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$ tree testing

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testing
|-- another
|   +-- wilma
+-- betty
+-- fred
+-- nested
    +-- barney

The destination is an empty directory named test_backup.

No Slashes

The first test has no slashes on any of the directories.

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$ rm -r test_backup/*
$ rsync --archive --recursive testing test_backup
$ tree test_backup

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test_backup
+--testing
   +-- another
   |   +-- wilma
   +-- betty
   +-- fred
   +-- nested
       +-- barney

You can see that the whole hierarchy of the testing directory has been recreated within the destination directory.

Slash on Destination Only

The second test, after clearing out the destination directory, adds a slash to the end of the destination directory.

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$ rm -r test_backup/*
$ rsync --archive --recursive testing test_backup/
$ tree test_backup

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test_backup
+--testing
   +-- another
   |   +-- wilma
   +-- betty
   +-- fred
   +-- nested
       +-- barney

So, there’s no difference there. A slash on the destination directory appears to have no effect.

Slash on Source Only

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$ rm -r test_backup/*
$ rsync --archive --recursive testing/ test_backup
$ tree test_backup

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test_backup
+-- another
|   +-- wilma
+-- betty
+-- fred
+-- nested
    +-- barney

This is different. The contents of the source directory have been duplicated into the destination directory.

Slashes on Both

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$ rm -r test_backup/*
$ rsync --archive --recursive testing/ test_backup/
$ tree test_backup

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test_backup
+-- another
|   +-- wilma
+-- betty
+-- fred
+-- nested
    +-- barney

And this one again shows that having a slash on the destination directory has no effect.