How to create a file for every directory on a tree?

Question

For the following tree structure:

    .
└── dir1
    └── dir2
        └── dir3

What would be a simple way to create a file (could be empty), for every directory, so the resulting tree will look like:

.
├── dir1
│   ├── dir2
│   │   ├── dir3
│   │   │   └── README
│   │   └── README
│   └── README
└── README

Stéphane Chazelas · Answer 1 · 2022-03-26T08:05:47.860

3

With zsh:

touch -- README **/*(N/e[REPLY+=/README])

It combines recursive globbing (**/*) with glob qualifiers, which here are:

Nullglob: doesn't trigger an error if there's no match.
/: restrict to files of type directory
e[code]: evaluates the code for each file, here appending /README to file path (stored in $REPLY in the evaluated code).

Or you could use an anonymous function which is passed the list of directories, and which appends the /README to each in the arguments it passes to touch:

() {touch -- $^@/README} . **/*(N/)

(with rc-style array expansion for the anonymous function @rguments using the $^array syntax).

In all those, you can add the Dotglob glob qualifier to also add README to hidden directories.

edited Mar 26 '22 at 08:05

answered Mar 25 '22 at 12:38

Stéphane Chazelas

544,893

Could you add an explanation to your answer? – mashuptwice Mar 25 '22 at 22:18
@mashuptwice, see edit. – Stéphane Chazelas Mar 26 '22 at 08:05

mashuptwice · Accepted Answer · 2022-03-25T12:27:51.280

2

You can do that with find:

find . -mindepth 1 -type d -exec touch "{}/README" \;

Explanation

-mindepth 1 will set the minimum depth, to avoid including the current directory
-type d will only find directories
-exec will run a command
{} contains the path of the found directory

If you want to use only builtin shell commands:

for dir in *; do if [ -d "$dir" ]; then touch "$dir/README"; fi; done

Explanation

for will loop over every element in *, meaning all files in the current directory. dir will contain the current element during the loop.
if [ -d $dir ] checks if the element is a directory and only then
creates a file called README in the directory name contained in $dir

edited Mar 25 '22 at 12:27

answered Mar 24 '22 at 20:37

mashuptwice

1,383

Note that arguments that include (contain) {} as a substring are not guaranteed to work. – G-Man Says 'Reinstate Monica' Mar 25 '22 at 06:36
@G-ManSays'ReinstateMonica' could you name one example where that would fail? – mashuptwice Mar 25 '22 at 12:32
I can’t give specific examples where it would fail, but see (1) Wildcard’s answer — scroll down to “find in combination with sh” and read the second bullet. Or see (2) jlliagre’s comment on my answer. … (Cont’d) – G-Man Says 'Reinstate Monica' Mar 25 '22 at 20:43
(Cont’d) … In an attempt to get specific, I’d say that you’re depending on behavior that may be unique to GNU find, so you’d be in danger on any busybox-based system (e.g., ESXi), or on non-Linux systems like *BSD, HP-UX, Solaris, etc. – G-Man Says 'Reinstate Monica' Mar 25 '22 at 20:43

How to create a file for every directory on a tree?

2 Answers2