File Management

Introduction

• Typically, files in a file system are organized and associated with several file attributes, including the file name, size, creation and modification timestamps, permissions, and file type. These attributes provide detailed information about the file and determine how it can be accessed and manipulated.
• In file management, directories (also known as folders) are used to organize/store, and group related files. They create a hierarchical structure that helps users and applications navigate and locate files. Directories can contain both files and subdirectories, allowing for a structured organization of data. They allow users to group related files together and create a logical structure. Directories can be nested within other directories, forming a tree-like structure.
• Understanding file attributes is essential for efficient file system management and operating system design, ensuring security, access control, and optimized use of storage.

Definition

• In an Operating System (OS), a file is a collection of related information stored on secondary storage, such as a hard disk, SSD, or flash drive. 
• File management in an operating system (OS) refers to the processes and tools used to organize, store, manipulate, control, and retrieve files and directories on a computer. It involves tasks such as creating, deleting, copying, moving, and searching for files, as well as managing file permissions and access control.

File Attributes

• File attributes are metadata associated with files that help the OS and users manage, access, and secure files properly.
• File attributes help manage files on secondary storage systems such as:
  • Hard Disk Drives (HDD)
  • Solid State Drives (SSD)
  • Optical disks
  • USB drives
• The OS uses file attributes to:
  • Keep track of file locations and sizes.
  • Perform access control depending on user and permission attributes.
  • Index and search files efficiently.
  • Maintain data integrity and backup systems.
• Each file stored in a filesystem has a set of attributes that describe its properties. These are –
  • Name
    • It is the human-readable identifier for the file.
    • It is used in the Identification of the file
    • For example: document1.txt, image1.jpg.
    • This attribute is used to access or manage the file.
  • Identifier
    • It is a unique tag or number (usually an index or inode) used internally by the OS to identify the file.
    • It supports internal tracking, not visible to users.
  • Type
    • This attribute indicates the nature or format of file contents.
    • It recognizes the format or usage of the file.
    • For example: .txt, .pdf, .jpg, .exe, etc.
    • This attribute helps the OS or user applications open files with the suitable program.
  • Location

• • Protection (Permissions)
    • This is the security setting or Access control for users that defines who can read, write, or execute the file during operations or activities.
    • This protection can be applied to different types of users: Owner, Group, and Others, and in different modes: Read (r), Write (w), Execute (x).
    • For example (Linux): rwxr–r– (Owner can read/write/execute; others can read only).
  • Flags
    • This is the special indicator that enables or restricts file operations, hence called behaviour indicators.
    • For example:-

• • Timestamps (Time and Date Information)
    • This attribute includes –
      • Creation Time – when the file was first created.
      • Last Modification Time – the last time the content was changed.
      • Last Access Time – the last time the file was read.
    • This Info tracks modification/access history.
    • This attribute is essential for version control, backups, and file synchronization.
  • 9. Owner and Group
    • This attribute enables multi-user management and security.
    • This attribute helps in implementing file security and user access control, and includes –
      • Owner: The user who created or owns the file.
      • Group: A collection of users with shared access rights.

File Types

• In an operating system, file types refer to the different kinds or formats of files stored on a computer or any secondary storage device like a hard drive or USB.
• Each file type has a specific structure and is used for a particular purpose, like storing text, images, audio, or programs.
• File types are usually identified by their file extensions, such as .txt, .jpg, .mp3, or .pdf. These extensions help both the user and the system know which application should open the file and how to handle it.
• File types help both the operating system and users manage files effectively, especially on secondary storage.
• Understanding file types is important because it helps organize data, select the right software to open files, and manage storage effectively. On secondary storage, file types also help the operating system read and write data properly.
• For example:
  • A .txt file is a simple text file that can be opened with Notepad.
  • A .jpg file is used for images and can be opened with a photo viewer.
  • A .mp3 file stores audio and is played using a music player.

• On secondary storage devices like HDDs, SSDs, and USBs:

  • Files are stored with metadata that includes the file type.
  • File types affect how data is written, stored, and retrieved.
  • OS and applications use file extensions to determine how to handle a file.
• File types help users to identify content and open it with the appropriate tools.
• Using this, the OS knows whether the file is executable or needs an interpreter.
• By knowing file types, systems can warn about potentially harmful types like .exe.
• By knowing file types, file extensions help in categorizing during searches.
  

• Classification of File Types

  We can group file types into categories, which are as follows:

File Operations Activities

• The OS provides various operations for managing files, such as creating, opening, closing, reading, writing, deleting, copying, moving, renaming files, etc. These operations are typically performed through system calls or higher-level file management APIs.
• The file system is the underlying structure in an operating system that manages how files are stored, named, and accessed on a storage device (such as a hard drive or SSD). Some common file systems of operating systems are NTFS (Windows), HFS+ (Mac), and ext4 (Linux).
• There are specific file management features and tools available for operating systems that may vary depending on the operating system we’re using. But some common file operations are usually seen in file management activities by an OS, which is given as follows:- 

• • File Operations:
    • Creating Files: Users can create new files and specify their names, types, and locations. Applications can also create files to store data.
    • Deleting Files: Files can be permanently removed from the file system.
    • Copying Files: Files can be duplicated, creating a new copy in a specified location.
    • Moving Files: Files can be relocated within the file system, including moving them between directories or storage devices.
    • Modifying Files: The content of files can be modified as needed.
    • Renaming Files: File names can be changed without modifying the file’s contents.
  • File Access, Permissions, and Security:
    • The OS enforces access control mechanisms to protect files from unauthorized access. Permissions, such as read, write, and execute, can be assigned to users or groups, specifying who can perform specific operations on a file.
    • File permissions determine who can read, write, and execute files, and they can be set for individual users or groups.
    • File management includes controlling access to files and ensuring data security. 
  • File Metadata:
    • Along with file attributes, file systems can store additional metadata about files, such as file ownership, access control lists (ACLs), extended file attributes (e.g., file tags or comments), and file indexing information (e.g., for fast searching).
  • File Searching & Retrieval:
    • OSes often provide mechanisms to search for files based on various criteria, such as file names, file types, or specific content within files. This allows users to quickly locate files on their systems.
    • Search capabilities may be integrated into the file explorer or provided through dedicated search tools.
  • File Compression and Encryption:
    • OSes may support file compression to reduce storage space and file encryption to protect sensitive data. Compressed files are typically smaller and need to be decompressed before use, while encrypted files require decryption using an appropriate key or password.
    • Common file compression formats include ZIP, RAR, and GZIP.
  • File Backup and Recovery:
    • Backup and recovery mechanisms enable users to create copies of important files or the entire file system to protect against data loss.
    • OSes may provide built-in backup utilities or rely on third-party software for this purpose.
    • Regular backups create copies of files that can be restored in case of accidental deletion, hardware failures, or other issues.
  • File System Maintenance:
    • OSes often include tools to perform routine file system maintenance tasks, such as disk defragmentation (reorganizing fragmented files for improved performance) and disk error checking and repair.
  • File Sharing:
    • Some operating systems support file sharing, allowing users on the same network to access files stored on remote computers. This facilitates collaboration and file exchange between users.