Linux - Commands.txt

*******Linux Commands******

--> PWD : Present Working Directory

--> ctrl+L : Screen Clear

--> clear : Clear the Screen

--> ls : list of folders --> specifies what are folders in it

--> ctrl+c : exit from the shell (environment)

--> exit : exit from the shell (environment)

--> ll : to do long listing detailed information of the file and folder

--> D : Represents directory

--> -rwx : Represents file
s

--> Mkdir : To create Directory
   Example : mkdir <name>

--> Mkdir -p dir1/dir2/dir3 : To create Directory inside the directory
   Example : Mkdir -p dir1/dir2/dir3

--> up arrow : To get the older commands

--> CD : To get inside the directory "Change Directory"
   Example : CD <name>

--> CD  : To come out of the directory 
   Example : cd 

--> CD - : To go to previous directory
   Example : cd -

--> CD space .. : To come out of the directory 
   Example : cd ..
cal 
--> Touch : To create a empty file
   Example : Touch <file name>

--> : To create 10 files at a time
   Example : touch file{1..10} 

--> cat or more : To read the file
   Example : cat <file name> or more <file name>
ls

--> : cat>dir1/dir2/dir3/dir4/<filename> 
      Hello World -> data created in filename in dir4

--> : Creating link : suppose having a directory aws in the directory i have file named file1
      Example : ln -s file1 /root/clouds/aws-link    
               Here : root is the user
                    : clouds is another folder like aws 
                    : aws-link is the link name for file1 in clouds folder
               Now  : go to CD clouds
                    : ll  ll -s
                    : you will see the link created in the clouds folder
              --cat <linkname>

--> : vim : To edit the data inside the file 
        Example : vim <file name>
 
        i : Insert mode to edit file
        Example : <Type> mkdfsojdkojaskdlkasdldaksldl(data)

        ESC : To come out from edit mode or Insert Mode

        wq : save & quit

--> I (Capital I) : i want to go to starting of that line ,inside the file (data) if my cursor is at the end or middle  
                    (make sure you are in ESC mode NOT in  insert mode while performing this operation)

--> A (Capital A) : i want to go to END of the line ,inside the file (data) if my cursor is at the first or middle  
                   (make sure you are in ESC mode NOT in insert mode while performing this operation)

--> O (Capital O) : inserts a new line on top from a present line
                   (make sure you are in ESC mode NOT in insert mode while performing this operation)

--> o (small o) :  inserts a new line on down from a present line
                   (make sure you are in ESC mode NOT in insert mode while performing this operation)

--> Command Mode

--> shift+g  :  cursor will move to bottom of the file inside the file

--> gg  :  cursor will move to top of the file inside the file

--> yy  :  to copy the single line inside the file

--> P  :  to paste the copied line inside the file

--> U  :  undo

--> shift+:set num  : To set no. for the lines inside the file

--> :83  : cursor will point to 83 line 

--> / : to search particular word in a afile 
    example : /today 

--> visudo : to practise above commands

--> ESC : To come out from edit mode or Insert Mode

--> vi : To open the file & also to create the file and open
   Example : vi <file name>

--> i : Insert mode to edit file
   Example : <Type> mkdfsojdkojaskdlkasdldaksldl(data)

--> ESC : To come out from edit mode or Insert Mode

--> :wq! : To write --> save & quit

--> cp : coping data from one file to another file  
   Example : cp file1 file2  -> what ever the data in file1 will copy to file2

--> cp : copies the files from one directory to another directory
   Example : cp /home/cloudera/<directoryname>/<filename>  /home/cloudera/<directoryname>/<filename> (Absolute path)

--> rm : To remove the file in directory
   Example : rm <filename>

--> rm -f  : To remove the file in directory without permission
   Example : rm -f <filename>

--> rmdir : To delete the directory
   Example : rmdir <directory name>

--> rm -rf : To remove directory with file (recurssive remove)
   Example : rm -rf <directoryname>

--> rm -rf * : To delete all files 
   Example   : rm -rf * <directoryname>

--> rm -rf f* : To delete files name starts with F (recurssive remove)
   Example    : rm -rf f* <directoryname>

--> :q : only to quit with out saving the write

--> ***********Absolute path************
   Example : /home/cloudera/<directory>/<filename>

--> *************Relative path**********
   Example : mkdir <directoryname>

--> : ls -al : list of hidden files

--> TO insert data into file there are two way :

1.Static way :  CAT
                ECHO
                SED

2.Dynamic way : VIM
                NANO

  Static Example : Cat>file1 ex : file1 is a file name
                   This is my file-1 (enter data)
                   click -> Enter
                   Ctrl+d Saves the file.

--> : Cat>>file 1 ex : file1 is a file name
                       click -> enter
                       ctrl+d saves the file -> To add the data in the file without deleting older data in the file

--> : echo "hello world" > file3 -> it will print the data and data is saved in file3
                        -> "Hello World" is a data inside the file
                        -> file3 is the file name

--> : mv file1 file5 -> to change the file name from file1 to file 5

--> : yum install tree -y  -> it will install the package 
    : Tree -> display's the structure of the the directory ex : how many directories and files are exist

--> : touch dir1/dir2/dir3/dir4/<filename> --> file will be created under dir4

--> : vim -o file1 file2 --> differentiate between two files in horizontal view

--> : vim -O(Captial O) file1 file2 --> differentiate between two files in vertical view

--> : diff file1 file2 --> differentiate only data between two files 

--> : :qa to come out of vim -O file3 file4 mode

--> File Permissions

--> -rw : - means regular file

--> b : blocked file

--> c : character file

--> d : directory

--> i : link file

--> rw- : (rw-) first part USER   :6

--> r-- : (r--) second part Group :4

--> r-- : (r--) third part others :4

--> : r : Read    : 4

--> : W : Write   : 2

--> : X : Execute : 1  (the file name shows in green when the permission are assigned as executabel)

--> To give the permission to a file (first method)
    Example [root@ip-172-31-28 ~]# chmod 765 file 1
     7 -> user having read 4 write 2 execute 1 permissions total 7
     6 --> user having read 4 write 2 permissions total 6
     5 --> user having read 4 execute 1 permissions total 7

--> To give the permission to a file (Second method)
    Example [root@ip-172-31-28 ~]# chmod u=rwx,g=rx,o=rw file3

--> Change the ownership of the file from root user to thiru
    Example [root@ip-172-31-28 ~]# chown thiru file 1

--> Change the ownership of the file from root group to thiru
    Example [root@ip-172-31-28 ~]# chgrp thiru file 1

--> To Change the ownership of the file from root User AND root group to thiru at a time for both 
    Example [root@ip-172-31-28 ~]# chown thiru:thiru file 1

--> : To print top 10 lines
    Example : [root@.......~}# head file1 --> bydefault prints top 10 lines
    Example : [root@.......~}# head -7 file1 --> will print top 7 lines

--> : To print bottom 10 lines
    Example : [root@.......~}# Tail file1 --> bydefault prints bottom 10 lines
    Example : [root@.......~}# tail -6 file1 --> will print bottom 7 lines

--> : encryption -> to encript the file 
    Example : [root@.......~}# gpg -c file1 --> it will ask for password
    passpharse ********
    -> if you try to open the encrypt file, the file will open but content in the file will show different

--> : TO Dcrypt --> To dcrypt encrypted file
    Example : [root@.......~}# gpg -d file1.gpg

--> : To count the words in the file
   Example :  [root@...~]# WC file 1

--> : To know the directory size 
    Example :  [root@...~]# du -sh  -> it will display the size of the directory 
               du -> stands for disk usuage

--> : To know the file size 
    Example :  [root@...~]# du -sh file1 -> it will display the size of the file
               du -> stands for disk usuage