Types

Linux distinguishes 3 main categories of files:

  1. Regular files
  2. Directories
  3. Special files

The command:

file <file>

can be used to determine the type of a file

Special files

Under “special”, linux understands all files that are not regular. They are:

Character files

These files, usually located in the /dev directory, represent devices that interact serially with the operating system (e.g., a mouse or keyboard).

Block files

These are also normally located in /dev but represent block devices (devices that read and write data in fixed-size blocks, such as hard disks and RAM )

Links make it possible to reference the same file content from different paths, which is useful for flexibility, backup strategies, and file management.

  • Hard Links:

    • A hard link associates multiple filenames with the same block of data.
    • Both the original file and the hard link are indistinguishable at the filesystem level—they share the same inode number
    • Deleting one hard link does not remove the data until the last hard link is deleted.
    • Hard links cannot span across different filesystems or partitions.
    • Hard links do not work with directories (to prevent circular references).
    • Can be created with ln f1 f2 (Link from f2 to f1)

  • Soft links:

    • A symlink acts like a shortcut, pointing to another file
    • Deleting a symlink does not affect its target file.
    • If the target file is deleted or moved, the symlink becomes broken (dangling).
    • Modifying a symlinked file modifies the target file.
    • Symlinks can point across different filesystems.
    • Symlinks can refer to directories.
    • Can be created with ln -s f1 f2 (Link from f2 to f1)

Sockets

Sockets are special files that facilitate communication between different processes.

Named Pipes

Also known as FIFOs, these files allow one process to deliver its output directly to another using a unidirectional data flow.