GNU bug report logs - #61966
diff -r reports identical devices nodes (maj/min) as different

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Gioele Barabucci <gioele <at> svario.it>
To: bug-diffutils <at> gnu.org
Subject: diff -r reports identical devices nodes (maj/min) as different
Date: Sat, 4 Mar 2023 17:54:20 +0100

Dear diff developers,

an issue related to the way diff compares directories that contain 
device nodes has been reported in <https://bugs.debian.org/929896>.

In a nutshell, identical device nodes are reported as different, but 
only during recursive comparisons (`-r`).

The following steps can reproduce this issue:

    $ mkdir a; sudo mknod a/null c 1 3
    $ sleep 1
    $ mkdir b; sudo mknod b/null c 1 3
    $ diff a/null b/null ; echo $?
    0
    $ diff -r a b ; echo $?
    File a/null is a character special file while file
    b/null is a character special file
    1

(Device 1/3 is the null character device, i.e. `/dev/null`.)

Removing the `sleep 1` command reduces (but does not eliminate) the 
probability of getting this faulty behavior.

Regards,

-- 
Gioele Barabucci

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