How can only directories be listed, that do not have another child directory?
Imagine a structure like /A /A/AA /A/AB /A/AB/ABB /B /C /C/CC /C/CC/CCC /C/CC/CCC/CCCC I would like to use find to list only /A/AA /A/AB/ABB /B /C/CC/CCC/CCCC.
The starting point would be find . -type d, but neither -mindepth nor -maxdepth can be used, can -noleaf help (I could not get it to react the way I wanted it to)?
Here's a POSIX-compliant solution that postprocesses the output of find to remove directories that have a listed subdirectory. It assumes that there are no newlines in the directory names.
{ find . -type d; echo; } |
awk 'index($0,prev"/")!=1 && NR!=1 {print prev}
1 {sub(/\/$/,""); prev=$0}'
Explanation: the awk script delays the printing of each line until it's read the next line and only prints the previous line if it's not a prefix. This takes advantage of the fact that find lists subdirectories immediately after their parent. The extra "/" is to avoid spuriously removing foo when foobar also exists. The inelegant NR!=1 avoids printing an initial empty line, and the inelegant echo; is not to have an equally inelegant special case for the last line. The call to sub removes a trailing slash from the toplevel directory, in case e.g. find ./ was called.
As usual there's a cryptic zsh one-liner.
echo **/.(e\''test -z $REPLY/*(/DN[1])'\':h)
Longer, more readable version:
is_leaf () { [ -z $REPLY/*(/DN[1]) ] }
echo **/.(+is_leaf:h)
The last line can be simplified to echo **/(+is_leaf) if you dont' mind the trailing /.
Summary explanation: The stuff in parentheses are glob qualifiers, documented in the zshexpn man page. We filter the results of the glob **/ (expanding to the current directory and all its subdirectories), keeping only those for which the function is_leaf (or the code between '…') returns 0. The filter code globs the subdirectories of the match being tested ($REPLY) (in fact, [1] makes it stops after the first subdirectory) and returns a status indicating whether at least one subdirectory was found. The glob qualifier / restricts the expansion to directories; N means the expansion is empty if there is no match; D causes dot files to be included; :h is a history modifier and causes the /. suffix to be stripped (in general it means dirname).
Just to illustrate the possibilities of zsh's glob qualifiers, here are two other variants (longer and I think more obscure) with a corresponding is_leaf function:
echo **/.(e\''tmp=($REPLY/*(/DN[1])); ((!#tmp))'\':h)
echo **/.(e\''$REPLY/*(/DN[1]e:REPLY=false:)'\':h)
is_leaf () { set -- $REPLY/*(/DN[1]); ((!#)); }
is_leaf () { return $REPLY/*(/DN[1]e:REPLY=1:) }
mkdir -p A/AA; { find A/ -type d; echo; } | awk 'index($0,prev"/")!=1 && NR!=1 {print prev} 1 {prev=$0}' will output A/ as well as A/AA. I could not test the zsh yet...
– MaoPU
Oct 6 '10 at 13:05
/; the code would have worked with find A or find /A. I've fixed my answer. There's still a very uncommon edge case that's not right (if you run the code in a filesystem with no directory other than the root, you get an empty line instead of a line with /). Change the awk print statement accordingly if you care about this bug. I've also found a slightly simpler zsh version (it's almost readable now).
– Gilles
Oct 6 '10 at 18:29
** globbing, so there might be a way to write one of those neat one liners in bash, too. Since the original question suggested the usage of find and the awk script is fairly readable, I went basically for this solution and added leaf () { { find -- "${1:-.}" -type d; echo; } | awk 'index($0,prev"/")!=1 && NR!=1 {print prev} 1 {sub(/\/$/,""); prev=$0}'; } to my .bashrc. Thank you.
– MaoPU
Oct 6 '10 at 19:21
**, so you don't need find, but you still need some other way of filtering out the non-leaf directories. You can use a for loop over **/., but it's not really one-liner material.
– Gilles
Oct 6 '10 at 19:43
This is what I use:
leaf () { find "${1:-.}" -depth -type d | sed 'h; :b; $b; N; /^\(.*\)\/.*\n\1$/ { g; bb }; $ {x; b}; P; D'; }
Call it using the directory to start from:
leaf /start/dir
s), especially since the hold space is particularly appropriate here. (Note that the semicolon isn't POSIX and may have to be replaced by newlines outside Linux.) But I couldn't upvote an unquoted variable substitution! (And there's still the problem of an argument whose name begins with -, which is a general find annoyance.)
– Gilles
Oct 5 '10 at 22:56
s (just joking, right?) Just to understand this: What is the problem of an unquoted variable substitution? None of my test cases broke the script. Anyway, is there a solution for the names starting with - (don't see a general find solution to this in your answer neither)?
– MaoPU
Oct 6 '10 at 12:54
- (such as a directory called -print), I think if you have a single path and believe in the implementer scrupulously following a 21st-century version of POSIX, then find -- "${1:-.}" is good enough. Otherwise you can preprocess the argument to prepend ./ if it starts with -.
– Gilles
Oct 6 '10 at 18:34
* (without quotes, the shell would expand the pattern) or foo bar (without quotes, the shell would split the argument into words).
– Gilles
Oct 6 '10 at 18:35
find -- to stop it from reading arguments, but it would not work. I think, to make it bullet proof, you need to test for relative or absolute paths and prepend a ./ in case it is a relative path.
– MaoPU
Oct 6 '10 at 19:17
