Explanation of *nix directory permission bits, with mnemonic devices

directory-perms.org

Mode	cd	ls	ls -l	cat	touch
--- 0
--x 1	x			x
-w- 2
-wx 3	x			x	x
r-- 4		x
r-x 5	x	x	x	x
rw- 6		x
rwx 7	x	x	x	x	x

• r lets you *read* the directory listing (ls)
• r with x lets you *read* an *extended* directory listing (ls -l)
• w alone is *worthless*
• w with x lets you *write* to files (touch)
• x lets you *examine* file contents (cat) and *exist* in the directory (cd)