File System Object

Nix implementations use a simplified model of the file system, which consists of file system objects. Every file system object is one of the following:

  • File

    • A possibly empty sequence of bytes for contents
    • A single boolean representing the executable permission

  • Directory

    Mapping of names to child file system objects

  • Symbolic link

    An arbitrary string. Nix implementations do not assign any semantics to symbolic links.

File system objects and their children form a tree. A bare file or symlink can be a root file system object.

Nix does not encode any other file system notions such as hard links, permissions, timestamps, or other metadata.

Examples of file system objects

A plain file:

50 B, executable: false

An executable file:

122 KB, executable: true

A symlink:

-> /usr/bin/sh

A directory with contents:

├── bin
│   └── hello: 35 KB, executable: true
└── share
    ├── info
    │   └── hello.info: 36 KB, executable: false
    └── man
        └── man1
            └── hello.1.gz: 790 B, executable: false

A directory that contains a symlink and other directories:

├── bin -> share/go/bin
├── nix-support/
└── share/