Unix: Visual QuickStart Guide

Translating mnemonic permissions to numeric permissions

The permissions for a file, as you've seen throughout this chapter, come in sets of three—rwx, for read, write, and execute permissions. And, as we showed you, you set these permissions by specifying that each one is either "on" or "off." For example, ugo+rwx sets read, w rite, and execute permission to on for u ser, group, and other, while a+rw sets read and write to on for everyone and a-x sets execute to off (indicated in directory listings with the -).

Rather than setting permissions with letters and hyphens, however, you can translate them into numeric values, using 1 for on and 0 for off. So, rw-, with read and write on and execute off, would translate into the numbers 110. You could ...