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03.Linux_File_Types.md

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Types of Files in Linux

In Linux, everything is treated as a file. All files are divided into three types:

  1. Normal files or ordinary files
  2. Directory files
  3. Device files

{A} Ordinary Files

  • These files contain data, which can be either text or binary (e.g., video, image, audio).

  • Examples:

    • abc.txt
    • index.html
    • test.java
    • test.py
    • script.sh
    • image.jpg
    • song.mp4

  • In Linux, file extensions are not important; Linux identifies file types based on their content.

    • Example:

      touch img.jpg
ls -l img.jpg
file img.jpg
gedit img.jpg   # Add some content to it
cat img.jpg
file img.jpg
      akshay@Ubuntu:~/Documents/DurgaSoft_Linux$ touch img.jpg
akshay@Ubuntu:~/Documents/DurgaSoft_Linux$ ls -l img.jpg
-rw-rw-r-- 1 akshay akshay 0 Aug 30 14:31 img.jpg
akshay@Ubuntu:~/Documents/DurgaSoft_Linux$ file img.jpg
img.jpg: empty
akshay@Ubuntu:~/Documents/DurgaSoft_Linux$ gedit img.jpg
akshay@Ubuntu:~/Documents/DurgaSoft_Linux$ cat img.jpg
Added some content to it
akshay@Ubuntu:~/Documents/DurgaSoft_Linux$ file img.jpg
img.jpg: ASCII text

  • Renaming img.jpg to img.durga:

    akshay@Ubuntu:~/Documents/DurgaSoft_Linux$ mv img.jpg img.durga
akshay@Ubuntu:~/Documents/DurgaSoft_Linux$ file img.durga
img.durga: ASCII text

{B} Directory Files

  • These files represent directories.
  • In Windows, the term "folder" is used, while in Linux, the term "directory" is preferred.
  • A directory can contain files and subdirectories.

{C} Device Files

  • In Linux, every device is represented as a file, allowing communication with the device.
  • Device files in Linux represent hardware devices, such as hard drives, keyboards, and network interfaces.
  • They are located in the /dev/ directory.
  • Two main types: character devices (for sequential data) and block devices (for random access).
  • Accessing device files through system calls allows interaction with hardware.

    • Example:

      tty  # This file represents the terminal
      • External terminal: 
        akshay@Ubuntu:~/Documents/DurgaSoft_Linux$ tty
/dev/pts/0
      • VSCode terminal: 
        akshay@Ubuntu:~/Documents/DurgaSoft_Linux$ tty
/dev/pts/1

    • Sending output from one terminal to another:

      • First terminal:

        akshay@Ubuntu:~/Documents/DurgaSoft_Linux$ tty
/dev/pts/0
akshay@Ubuntu:~/Documents/DurgaSoft_Linux$ echo "Hello I am in first terminal"
Hello I am in first terminal
akshay@Ubuntu:~/Documents/DurgaSoft_Linux$ echo "Hello I am in first terminal" > /dev/pts/1

      • Second terminal:

        akshay@Ubuntu:~/Documents/DurgaSoft_Linux$ Hello I am in first terminal

      • Clearing output on the second terminal:

        akshay@Ubuntu:~/Documents/DurgaSoft_Linux$ clear > /dev/pts/1

Shortcut Commands for Terminal

  • Open terminal: Ctrl + Alt + T
  • Close terminal: Ctrl + D

How to Check File Type

  • In Ubuntu, blue-colored files represent directories, while other colors represent normal files. However, this color convention varies by distribution, so it is not a standard method.

  • Use the ls -l command to check file types.

    total 4576
-rw-rw-r-- 1 akshay akshay     342 Aug 29 07:52  directory-hierarchy-linux.mermaid
-rw-rw-r-- 1 akshay akshay 4633146 Aug 28 11:05 'DurgaSir Linux.pdf'
-rw-rw-r-- 1 akshay akshay     463 Aug 29 07:15  flow-example.mermaid
-rw-rw-r-- 1 akshay akshay      25 Aug 30 14:32  img.durga
-rw-rw-r-- 1 akshay akshay     300 Aug 28 18:39  index.html
-rw-rw-r-- 1 akshay akshay      58 Aug 28 10:58  README.md
-rw-rw-r-- 1 akshay akshay     367 Aug 28 11:42 'Session 01.Intoduction.txt'
-rw-rw-r-- 1 akshay akshay    4870 Aug 29 08:04 'Session 02.Components of Unix & Execution Flow.txt'
-rw-rw-r-- 1 akshay akshay    3086 Aug 30 14:54 'Session 03.Linux File Ststem.txt'
-rwxrw-r-- 1 akshay akshay      50 Aug 28 19:11  test.sh
-rw-rw-r-- 1 akshay akshay     672 Aug 28 18:26  unix-flow-digram.mermaid
-rw-rw-r-- 1 akshay akshay     710 Aug 28 19:43  user-os-hardware.mermaid