A Mnemonic for Changing Modes

Making a script file executable involves an incantation that has something to do with chmod but what exactly? chmod has two modes, absolute and symbolic. In absolute mode, you set the entire set of permissions with a numeric value like 755.

In symbolic mode, you can add or subtract permissions to either the user (u), group (g) or owner (o). To give read permissions to the group type:

> chmod g+r myfile.txt

And to give execution priviledges to the owner of a file:

> chmod o+x myscript.rb

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