Why does GNU find suppress printing -prune'd directories when another "-or" test is applied?

Question

I have a directory with the following files and a .git directory, e.g.

.
├── .git
│   ├── branches
│   ├── COMMIT_EDITMSG
│   ├── packed-refs
│   └── refs
├── readme.md
├── server_build.sh
└── tags

If I run GNU find command with the -prune test, find prints the directory which is prune'd:

% find . -name '.git' -prune
./.git

If add another OR option, then the directory which is pruned not longer appears in the output:

% find . -name '.git' -prune -o -name '*.md' -print
./readme.md

In this case, both -name '.git' and -name '*.md' tests must be returning true, it can't be possible that adding another OR test suddenly makes the -name '.git' -prune test untrue.
Is there some implicit switch being added to the first statement?
In other words is find turning

find . -name '.git' -prune

into

find . -name '.git' -prune -print

at run time? and the implicit -print is taken away when the next test when is added?
Why doesn't find print the -prune'd directory when another "-or" test is applied?

try find . \( -name '.git' -prune -o -name '*.md' \) -print also there is some discussion on this in man find just before EXIT STATUS — Sundeep, Jul 19 '16 at 06:10
find . -name '.git' -prune prints .git because there is no other action. On the other hand, find . -name '.git' -prune -o -name '*.md' -print is actually equivalent to find . \( -name '.git' -prune \) -o \( -name '*.md' \) -a -print, and -prune no longer prints anything since there is another action. — Satō Katsura, Jul 19 '16 at 06:23
@SatoKatsura I thought -prune was an action, and therefore the implicit -print would not be used here. — the_velour_fog, Jul 19 '16 at 06:26
From the manual: If the expression contains no actions other than -prune, -print is performed on all files for which the expression is true. — Satō Katsura, Jul 19 '16 at 06:30

score 1 · Answer 1 · answered Jul 19 '16 at 08:41

1

find . -name '.git' -prune

is the same as

find . -name '.git' -prune -print

so it prunes and then prints

find . -name '.git' -prune -o -name '*.md' -print

is the same as

find . \( -name '.git' -prune -true \) -o \( -name '*.md' -print \)

so it does first clause, if it does prune then it does true (prune returns true), and does not do right hand side of -o

These will always print

find . \( -name '.git' -prune -o -name '*.md' \) -print
find . -name '.git' -prune -print -o -name '*.md' -print

answered Jul 19 '16 at 08:41

ctrl-alt-delor

27,993

ah I think I understand. So its possible to perform TWO actions on matching files. so find . -name '.git' -prune -print is the same as find . -name '.git' -a -prune -a -print .? and -print would not happen if prune returned false? – the_velour_fog Jul 19 '16 at 08:49
@the_velour_fog yes. – ctrl-alt-delor Jul 19 '16 at 09:09
thanks, although in your answer where you say find . -name '.git' -prune -o -name '*.md' -print is the same as find . \( -name '.git' -prune -true \) -o \( -name '*.md' -print \) and and does not do right hand side of -o. the right hand does get run - its the only statement that produces output. i.e. output is: ./readme.md – the_velour_fog Jul 19 '16 at 09:33
1

Yes rhs should get evaluated when not -name '.git'. – ctrl-alt-delor Jul 21 '16 at 11:36

Why does GNU find suppress printing -prune'd directories when another "-or" test is applied?

1 Answers1