File and File System

FILE:

The file is a container for storing information.

Unix treat all as file example directory, device, file

three types of files:

ordinary file --- storing information

directory file --- Its directory contains files and other directories, But strictly speacking it contains names and number associated with each name.

device file: all devices and peripherals are represented by files. To read or write device

File System

Change Directory: cd

The tilde (the wavy horizontal line character) is used to represent users' home directories on Unix-like operating systems.

cd ~

cd command in Linux/Unix

cd is a Linux command to change the directory/folder of the terminal's shell.

You can press the tab button in order to auto complete the directory name.

cd syntax

cd examples

cd syntax

$ cd [directory]

cd command examples

Change to home directory (determined by $HOME environment variable):

$ cd

Also change to home directory:

$ cd ~

Change to root directory:

$ cd /

Change to parent directory:

$ cd ..

Change to subdirectory Documents:

$ cd Documents

Change to subdirectory Documents/Books:

$ cd Documents/Books

Change to directory with absolute path /home/user/Desktop:

$ cd /home/user/Desktop

Change to directory name with white space - My Images:

$ cd My\ Images

Or

$ cd "My Images"

Or

$ cd 'My Images'

Present Working Directory: PWD

pwd - print working directory, is a Linux command to get the current working directory.

pwd syntax

pwd examples

pwd syntax

$ pwd [option]

pwd command examples

Change directory to /usr/src directory and print working directory:

$ cd /usr/src

$ pwd

/user/src

Change directory to home directory and print working directory:

$ cd ~

$ pwd

/home/user

Change directory to parent directory of the home directory and print working directory:

$ cd ~/..

$ pwd

/home

Change directory to root directory and print working directory:

$ cd /

$ pwd

/

Home Directory:

A home directory, also called a login directory, is the directory on Unix-like operating systems that serves as the repository for a user's personal files, directories and programs. It is also the directory that a user is first in after logging into the system.

There are several easy ways for a user to return to its home directory regardless of its current directory (i.e., the directory in which it is currently working in). The simplest of these is to use the cd (i.e., change directory) command without any options or arguments (i.e., input files), i.e., by merely typing the following and then pressing the ENTER key:

MKDIR: make directory

Syntax: mkdir foldername

  

mkdir sample

multiple Directories: mkdir a b c

Sub directories: mkdir -p a/b/c

-p Parental

Remove Directory: RMDIR

Syntax: rmdir foldername

  

rmdir sample

multiple Directories: rmdir a b c

remove only c folder rmdir a/b/c

Sub directories: rmdir -p a/b/c   (removes all directoires)

-p Parental

Listing Files:

ls command in Linux/Unix

ls is a Linux shell command that lists directory contents of files and directories.

ls syntax

ls options

ls examples

ls code generator

ls syntax

$ ls [options] [file|dir]

ls command options

ls command main options:

option description

ls -a list all files including hidden file starting with '.'

ls --color colored list [=always/never/auto]

ls -d list directories - with ' */'

ls -F add one char of */=>@| to enteries

ls -i list file's inode index number

ls -l list with long format - show permissions

ls -la list long format including hidden files

ls -lh list long format with readable file size

ls -ls list with long format with file size

ls -r list in reverse order

ls -R list recursively directory tree

ls -s list file size

ls -S sort by file size

ls -t sort by time & date

ls -X sort by extension name

ls command examples

You can press the tab button to auto complete the file or folder names.

List directory Documents/Books with relative path:

$ ls Documents/Books

List directory /home/user/Documents/Books with absolute path.

$ ls /home/user/Documents/Books

List root directory:

$ ls /

List parent directory:

$ ls ..

List user's home directory (e.g: /home/user):

$ ls ~

List with long format:

$ ls -l

Show hidden files:

$ ls -a

List with long format and show hidden files:

$ ls -la

Sort by date/time:

$ ls -t

Sort by file size:

$ ls -S

List all subdirectories:

$ ls *

Recursive directory tree list:

$ ls -R

List only text files with wildcard:

$ ls *.txt

ls redirection to output file:

$ ls > out.txt

List directories only:

$ ls -d */

List files and directories with full path:

$ ls -d $PWD/*