Ubuntu – Symbolic equivalent of chmod 600

chmodpermissions

The following is often used to set file permissions, a good example being setting a key file to an appropriate permission level to be used by ssh (this being the "octal" form):

chmod 600 filename.xyz

Would it be a correct equivalent and acceptable practice to use the following instead (this is the "symbolic" form)?

chmod a=,u=r filename.xyz

The reason I ask is that it seems a bit clearer for code readability. Still not exactly human readable, but no bit mapping needed.

If maximum readibility (and not terseness) were the primary driver, would there be a better option?

Best Answer

With a=,u=r, the order is important. If you accidentally swap the order of a= and u=r (or the order of a= and u=), the result would be very different. (Yes, a and u are pretty far from each other on a QWERTY keyboard, but someone looking at a reference doc and manually typing things in might mess up between the two very similar looking parts.) For maximum readability and safety, I'd be more explicit:

chmod u=r,go-rwx filename # or go-rwxst

The permission components are very different here, and way more explicit, making mistakes less likely to happen. And it doesn't matter if you have go-rwx first or u=r first.

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