shell: Different path patterns

Question

What is the difference among following path patterns in Linux

• ./ e.g. cp ./ [destination-path]
• ./. e.g. cp ./. [destination-path]
• ./* e.g. cp ./* [destination-path]
• ./** e.g. cp ./** [destination-path]

Answer 1

The first two would make more sense with a recursive copy, i.e. cp -r. The difference comes up if the source is a named directory, and the destination exists. Of these:

cp -r src/  dest
cp -r src/. dest

the first would copy src into dest, creating dest/src and files within it (src/a becomes dest/src/a), while the latter copies the contents of src, so src/a becomes dest/a.

In the other two, the shell expands the glob, so the contents of the directory (except dotfiles) are copied even without -r.

cp ./*  dest
cp ./** dest

In the first, the shell expands ./* to the list of filenames in the current directory (except those starting with a dot), and cp copies them. In the second, shells supporting it would expand ./** to a recursive listing of filenames, and again cp would copy the files it was listed.

The recursive ** works at least in Bash if shopt -s globstar is set, in ksh with set -o globstar.

Neither Bash or ksh includes files or directories with names starting with dot in the result of **, regardless of which level in the tree they appear, so using that is not a very good way to make a complete copy of a full directory structure; cp -r . dest would copy dotfiles too.

Bash has shopt -s dotglob which unhides dotfiles with both * and **, I'm not sure if ksh has a similar feature.