Tired of calculating symbolic and octal formats in your head? Download a dashboard widget that does the calculation for you. This is one sweet dashboard widget!
UNIX Permissions Calculator Dashboard Widget
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I highly recommend learning and using the letter specifiers. u=rwx,go=rx is the same as 755, but it's easier to communicate 'user can read write and execute,group and other can read and execute'. The '+' and '-' makes things easier too, because doing a 'u+w' means 'keep everything else the same, but add write permission to the user'. No required comparison of the current permissions versus the desired permissions.