Operating System Questions Medium
File permissions in a file system refer to the access rights or restrictions assigned to files and directories. These permissions determine who can read, write, or execute a file, as well as who can access or modify a directory.
In most operating systems, file permissions are based on a set of three categories: owner, group, and others. The owner is the user who created the file, the group consists of a collection of users, and others refer to everyone else.
There are typically three types of permissions that can be assigned to each category: read (r), write (w), and execute (x).
1. Read permission (r): Allows a user to view the contents of a file or list the files within a directory. For directories, read permission enables the user to access and view the names of files and subdirectories within it.
2. Write permission (w): Grants the user the ability to modify or delete a file, as well as create new files within a directory. For directories, write permission allows the user to add or remove files and subdirectories.
3. Execute permission (x): Enables the user to execute or run a file if it is a program or script. For directories, execute permission allows the user to access and enter the directory, provided they have read permission as well.
These permissions can be represented using a combination of letters or numbers. For example, "rwx" represents read, write, and execute permissions, while "r--" indicates read-only access. Additionally, numeric values can be assigned to each permission, with 4 representing read, 2 representing write, and 1 representing execute. These values can be added together to assign a numeric permission value to a file or directory.
File permissions are crucial for maintaining security and privacy within a file system. They ensure that only authorized users can access or modify files, protecting sensitive information and preventing unauthorized actions.