Create Linux-commands.md

Author: devcloudyy

shell-scripts/Linux-commands.md

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+# Linux Commands
+
+## Shell
+
+Shell => All the commands are fire on shell. The shell is working because it is fetching our all commands are providing the output.
+
+### Some BRANDS in Shell
+
+* Bourne shell (sh)
+* Korn shell (ksh)
+* Bourne Again shell (bash)
+* zsh and many more
+
+## Commands
+- ``man 'utility_name'`` => Gives the manual of all command related to the given utilities
+- ``crtl + l``  => Clear the Screen
+- ``uname``     => Give the information what kind of system are you using
+- ``uname -a``  => All Details regardig information
+-  ``uptime``   => show how much long your system in up 
+
+## Shell Commands
+#### Basic Commands
+- ``cd directory_name``    => Change Directory forward
+- ``cd..``  => Change Directory backward
+- ``cd``   => It gone directly to home directory
+- ``mkdir`` => Create a Empty Directory
+- ``ls``    => Listing all file in current Directory
+- ``ls -l`` => It gives a long listing version in the current directory
+- ``alias ll='ls -l'``  => This command aliasing the ll to ls -l
+- ``ls -a`` => It gives all the files including hidden file
+- ``vim file_name`` or ``nano file_name``   => It is default texy editor
+    - In **vim** editor if you want to exit from this editor following the given steps:
+        - Press the **esc** key.
+        - At botton you see a **:** sign after this sign type **q**.
+        - (q for quit surely it has more command).
+        - Then Press **Enter** Key
+- ``date`` => It gives the current Day Date
+- ``cal``  => Gives Calander of the current Month.
+- ``w``    => Gives How many user are logged in your system.
+- ``whoami``    => It is useful to know from whoes credential you are logged in.
+- ``whereis utility_name``  => Gives the path of utility where it is install.
+    - It only gives the path of that program are properly install in your computer and their path are set correctly.
+
+#### Creating and Removing Commands
+- `` mkdir Directory_name`` => Creating a directory
+    - "-rw-r--r" = If permission staring with **-** then it is file
+    - "drwxr-xr-x" = If permission start with **d** then it is directory or folder 
+- `` rm -r directory_name ``    => It delete the directory which you have to pass.
+    - **-r** tends to recursively delete that folder
+    - Linux thing if you are deleting a directory then chances are high that it is surely contain more files and folder inside that directory.
+    - So it is deleting the recursivily deleting that folder.
+- `` touch file_name.extension ``   => It create a file
+
+- `` history`` => It gives the history of previously used commands
+    - ``history > file_name.txt`` => It redirect the history of commands into the file.
+- `` cat file_name ``   => It is allow us to read the file.
+    - ``head`` or ``tail`` => It is also allow us to read the file but only heading part (head) and footing part(tail)
+
+
+#### Permissions
+*Linux was designed to allow many users to access single system at the same time. Also fies need to be protected from each other.*
+-  PERMISSION => Basically there are three types of permission in Linux.
+    - Read
+    - Write
+    - Execute
+
+* How to read Permissions ?
+    * drwxr-xr-x    10  admin  staff 320    28 jul 23:04 admin
+        * **d** First word represent the which kind of file it is.(File[-], Directory[d])
+        * **rwx** Represent the creator permission like root,admin.
+        * **r-x** Represent the Groups permissions
+        * **r-x** Represent the User permissions.
+    * Number of the permissions:
+        * x = 4 (Execute)
+        * w = 2 (Write)
+        * r = 1 (Read)
+- `` chmod 755 filename  ``
+    - 7 = 4+2+1 => Gives all permission to **Creator**
+    - 5 = 4+1 => Gives the the Execute and Read Permission to **Group**
+    - 5 = 4+1 => Gives the the Execute and Read Permission to **User** 
+
+
+
+*Many Times if we want to install some packages or softwares in our Linux based OS we need a permission of higher authority to successfully installl that things for that we use **sudo** keyword before fire actual installations commands of that package*