I would tell it erases only files with a dot in their name. To remove only the directories inside /tmp, first find them:
Code:
find /tmp -mindepth 1 -type d -print0 | xargs -0 rm -rf
the option mindepth 1 excludes the /tmp directory itself. First try the find command without the option -print0 and without piping the output to xargs. If the resulting list of directories is exactly the list you want to remove, then you can safely apply the whole command.
command to delete folders on /tmp
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