What is the difference between octal notation and symbolic notation when setting file permissions in Linux?
Octal notation and symbolic notation are two different methods used to set file permissions in Linux. Both methods serve the same purpose of controlling access to files and directories, but they differ in terms of their syntax and ease of use.
Octal notation, also known as numeric notation, represents file permissions using a three-digit number. Each digit in the number corresponds to a specific permission: the first digit represents the owner's permissions, the second digit represents the group's permissions, and the third digit represents the permissions for others.
In octal notation, each permission is assigned a numeric value. The read permission is represented by the value 4, the write permission by the value 2, and the execute permission by the value 1. To calculate the numeric value for a specific set of permissions, you simply add the values together. For example, if you want to set read and write permissions for the owner, read-only permissions for the group, and no permissions for others, you would use the octal notation 640. Here, the owner has read and write permissions (4+2=6), the group has read-only permissions (4), and others have no permissions (0).
On the other hand, symbolic notation, also known as textual notation, represents file permissions using a combination of letters and symbols. It provides a more intuitive and flexible way to set permissions, as it allows you to modify existing permissions without having to calculate numeric values.
In symbolic notation, each permission is represented by a letter: 'r' for read, 'w' for write, and 'x' for execute. Additionally, the plus symbol '+' is used to add permissions, the minus symbol '-' is used to remove permissions, and the equal symbol '=' is used to set permissions explicitly.
To set permissions using symbolic notation, you specify the target (owner, group, or others) followed by the operation (add, remove, or set) and the permission(s). For example, to add execute permission for the owner and group, you would use the symbolic notation "+x" for the owner and group permissions. To remove write permission for others, you would use the symbolic notation "-w" for others. The resulting symbolic notation for these changes would be "u+x,g+x,o-w".
Octal notation represents file permissions using a three-digit number, where each digit corresponds to a specific permission. Symbolic notation, on the other hand, represents file permissions using a combination of letters and symbols, providing a more flexible and intuitive way to set permissions.
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