16.3) User Permissions

Column 1 is a mixture of ‘-‘, ‘d’, ‘r’, ‘w’, and ‘x’. Column 1 always has 10 digits and the first digit will often either be an ‘-‘ or a ‘d’. An ‘-‘ indicates that the name listed on the far right hand side in column 9 is a file and a ‘d’ indicates that it is a directory. Digits 2 through to 10 of column 1 controls the permissions over the files and by permissions I mean it determines what you allow people to do with the files or directories.

I will firstly describe the permissions for a file. Digits in columns 2-4 determine your permissions for the file listed on the right hand side. Digit 2 will be either a ‘-‘ or a ‘r’ which means you can either read the file (using an editor like emacs) or not if a ‘-‘ is present. Digit 3 will be either a ‘-‘ or a ‘w’ and the ‘w’ indicates you can write to the file (ie modify it) or ‘-‘ can’t modify it. Digit 4 has either an ‘x’ or a ‘-‘ and indicates it is an executable program that can run if it is an ‘x’ or not if it is a ‘-‘. Regular data files are not programs so will have a ‘-‘.