3.1.1.2. Sorts of files

3.1.1.2. Sorts of files

Most files are just files, called regular files; they contain normal data, for example text files, executable files or programs, input for or output from a program and so on.

While it is reasonably safe to suppose that everything you encounter on a Linux system is a file, there are some exceptions.

• Directories: files that are lists of other files.
• Special files: the mechanism used for input and output. Most special files are in /dev, we will discuss them later.
• Links: a system to make a file or directory visible in multiple parts of the system's file tree. We will talk about links in detail.
• (Domain) sockets: a special file type, similar to TCP/IP sockets, providing inter-process networking protected by the file system's access control.
• Named pipes: act more or less like sockets and form a way for processes to communicate with each other, without using network socket semantics.

The -l option to ls displays the file type, using the first character of each input line:

jaime:~/Documents>ls -l total 80 -rw-rw-r--   1 jaime   jaime   31744 Feb 21 17:56 intro Linux.doc -rw-rw-r--   1 jaime   jaime   41472 Feb 21 17:56 Linux.doc drwxrwxr-x   2 jaime   jaime    4096 Feb 25 11:50 course/

This table gives an overview of the characters determining the file type: