Unix file permissions

There are two ways to represent Unix permissions:

  1. Symbolic notation
  2. Numeric notation

Symbolic notation
Consists of three sets of symbols called permission class.

  • First set represents User/Owner class
  • Second set represents Group class
  • Third set represents Others/everyone else class

Each set consists of 3 symbols each represents a permission:

  • “r” for read permission
  • “w” stands for write permission
  • “x” show execution permission

permission

Numeric notation
Consists of 3 sets of octal numbers to represent each permission component; owner, group, and others e.g. 777 or 745. Each octal number is the sum of its component bits in binary. Therefore;
1 –> execution permission
2 –> write permission
4 –> read permission
For example, 7 is 4 + 2 + 1 which means read & write & execution permissions. Or 6 is 4 + 1 which means read & execution permission.