chmod tutorial / cheat sheet / cheatsheet / for dummies
// Octal permissions: decimal, binary, 3-letter, English
0 = 000 = --- = none
1 = 001 = --x = execute (x)
2 = 010 = -w- = write (w)
4 = 100 = r-- = read (r)
// Combinations of the base octal permissions
3 = 011 = -wx = execute + write (1 + 2)