I'm sure I'm right with this. This was the way on Solaris and when I use 'man 2 chmod' on linux, I find the following sentence (translated from german):

     S_IXOTH   00001 Execute rights for others, on directories: others
+ are allowed to search directory
[download]

I also used this effect a few times to make dirs unreadable, but allowed the files in it to be read (security by obscurity, but better than nothing).

UPDATE: Sure I was, but wrong. As wrong as the man page.

I'm afraid ikegami is right on this one. For me, the magic of modes is one of the most confusing areas in *nix.

jth@reina:~/tmp/t$ ls -l
total 8
dr--r--r-- 2 jth jth 4096 2008-09-26 06:42 r
d--x--x--x 2 jth jth 4096 2008-09-26 06:42 x

jth@reina:~/tmp/t$ ls r
ls: cannot access r/file: Permission denied
file

jth@reina:~/tmp/t$ ls x
ls: cannot open directory x: Permission denied

jth@reina:~/tmp/t$ cat r/file
cat: r/file: Permission denied

jth@reina:~/tmp/t$ cat x/file
contents of x/file
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As you can see, r lets me list the file with ls (read the directory) but not access the file while x lets me access the file ("search") but not list the directory.

Don't feel too bad, I've been messing with modes for about 15 years and I still had to test to see who was right. Besides, you are completely correct when you say that one would almost always want rx on a directory.

I tested my claims on a linux system before posting. Maybe it's different on Solaris? (wow if true!) But it's more likely that "search" is a very poorly chosen name, because "r" is "read" for both files and directories. Linux refers to "x" on directories as "access".