Linux-Basic command

Table-content:

1.Terminal Cursor movement
2.Basic commands
3.Standard Streams in Linux

1.Terminal Cursor movement

i. Ctrl + A - move to the beginning of the lin e
ii. Ctrl + E - Move to the end of the line
iii. Ctrl + B -- Move backward one character
iv. Ctrl + F - move forward one character
v. Alt + B - Move backward one word
vi. Alt + F - Move forward one word
vii. Ctrl + R - Reverse search command history, Ctrl + R after press up Arrow.
viii. Ctrl + G cancel search history.
ix. Ctrl + L - clear the terminal
X. TAB - auto completion filename or command
xi. Ctrl + Z - stop the current command and resume wit fg in foreground or bg in background
xii. !! = repeat last command.

2.Basic commands

1.check current working directory

=> #pwd

output:-

/root

2.check current logged user

i. $ whoami- Display the username of currently logged in user.
ii.$ who - shows all logged user along with terminal sessions
iii. $ w - shows all logged user along with terminal sessions with activities.

3.chck the system hostname

i. $ hostname

ii. Show the detailed information about Hostname
$ hostnamectl
iii. check system ip & mac with help of hostname
$ hostname -I
(we will see, up coming blogs how to set the hostname temporarily and permanent)

4. check ip address

$ ip a
$ ip addr
$ ifconfig
(we will see, up coming blogs how to set the ip address ,gateway, broadcast,...etc, permanent and detailed result information)
5.clear the screen - $ clear

6.man = man is manual page of all command provide detailed documentation, syntax, options, example.

example:-

$ man ls

7.sudo
sudo is you allows you run command as super user ( admin privileges)

Example:-

$ sudo dnf update
- dnf is RHCL based package manger

8.$ history
-used to find out all those commands we ran previously.

9. create directory(folder)

`$ mkdir dir

$ mkdir dir1 dir2

$ mkdir -p grandpa/father/son

10 . Change directory

$ cd /home/user/Documents
$ cd .. => parent directory (move up one level in the directory structure)
$ cd . -> stay in the current directory
$ cd ../../ => move up multiple level.
$ cd - => go back to the previous directory
$ cd / = change root directory
$ cd ~ = change the home directory

11. Create file:-

i. create empty file using touch

$touch file.txt
$touch file.txt file1.txt

ii. Using echo

$echo "Welcome to MyLinuxBlog" > welcome.txt

iii. using cat

$cat > file.txt

Hi, this the text file(text somthing)
then Ctr + D(save)

iv. printf

$printf " Line-1 \n Line-2 \n Line-3 " > file.txt

12. List the file and directory

i. $ ls -lah
-l = list
-a = hidden
-h = human readable format
ii. $ ls -li
-i check inode for files and directory.
iii. $ ls -R
-R = recursively search (show the content of sub-ls directory)
iv. $ ls -ld */ (list the directory only)
v. $ ls -ld .. (parent)
vi. $ ls -ld . (current)

-t = sort by modification time

13. Copy the file and directory.

$ cp f1.txt destination-path/dirname

Example:-

$ cp file.txt dir1

Source to Destination copy:

$ cp file.txt /home/user/backup/

$ cp -r dir1 /home/user/backup/

Destination to Source copy:

$ cp /home/user/backup/file2.txt /home/user

option:-

-v verbose
-i = confirmation
-n = copy with without overwriting

14. Move and rename the file and directory

Rename the file:-

mv Oldname.txt Newname.txt

Move the file:-

mv file1.txt /home/usr/backup/

mv file2.txt file3.txt /home/user/backup/

option:-

-i - before moving ask confrimation.
-u -update
-v -verbose
-f force

*same method to follow directory move and rename.

when use mv the directory why do not use -r only using cp -r for dir ?

15. Delete the File and Directory

$rmdir dir1 (empty directory)
$rm -rfi dir (delete everything inside all directory )

option:-

-i - confirmation
-r - recusively
-v - verbose
-f - force
$rm -if file.txt

*-rf * = Be careful to use this option when deletion ,make to confirm once or four before use this option, can not retrieve the data after deletion.
rm -rf * ==> (* means all)Be careful

16. cat – display the content of the file

$cat > file.txt (it create the new file ,
it waits for you enter some text(owerites)
Ctrl + D(save)
$cat >> file.txt
appends to the file without overwriting existing content.
$cat -n file.txt -> Show with line numbers
$cat file1 file2 > merged.txt -> Merge files
$cat file.txt | grep "word" -> Search for a word
$tac file.txt -> Display in reverse.

17.more -Display the content page by page only navigation to forward direction not backward direction.

Example:

$more file.txt

Enter – scroll down one line
space – scroll down one page
-q - quite

$more +n file.txt
$more -n file.txt
n = number,

Example:-

$more +10 file.txt

18. less -Display the content page by page only navigation to forward direction and backward direction.

$less file.txt

output:-

hello welcome to Linux world
/search_word

example:
/Linux
space – scroll down one page
q - quite
b – scroll up up one page
g - go the begning of the file
G -go to end of the file.

19.head -display the first few lines, not real-time monitoring.

Example:-

$head f1.txt

$head -n 420 f1.txt

$head -c 20 f1.txt

-c display first 20 byte of the file content

20.tail-display the last few lines, real-time monitoring.

Example:-

$tail f1.txt
$tail-n 420 f1.txt
$tail -c 20 f1.txt

---

21. Standard Streams in Linux:-

1.stdin(0) - Takes input from the keyboard and file
2.stdout(1) -shows output like what you see on the screen
3.stderr(2) -shows error message ,also on the screen

1. Standard Streams

i. Standard Input (stdin - File Descriptor 0):

• Take the input from the user like keyboard, when run the cat, read command it required input , it wait for you type something other wise Ctr + D.

ii. Standard Output (stdout - File Descriptor 1):

*share the output on your screen like when you run echo, ls command .

Example:-

$echo "Hellow Linux world"

*echo command send to text stdout ,it displays on your screen.

iii. Standard Error (stderr - File Descriptor 2):

• send the error message on your screen
• when made mistake on terminal send the message stderr not for stdout.

Example:-

$cd dir1

*dir1 is not created really at the time error message sent to stderr.

2. Redirection in Linux: stdin , stdout ,stderr .

Example:-

i.Redirect Input (<):

• Input from the keyboard:

< -> Take the input from a file instead of the keyboard .
$ sort < names.txt
$ wc -l < nmaes.txt (wc -l -word count line)

• stdout (1) -Output to the screen: $echo "Welcome To My Blog" > file.txt

ii. Redirect Output (>):

$ echo "Hello" > file.txt
$ echo "Hello world" >> file.txt

iii. Redirect Errors (2>):

Example:-

$ls /usr/home/ 2> err.log

*/usr/home/ this actually not real path ,at the time error message sent to stderr.

output:

No such file or directory.

22.Pipe operator:-

• Pipe operator (|) connect multiple command.

syntax:-

command1 | command2

Example:-

$ ls | wc -l
$ cat file.txt | grep "Linux" (grep- pattern searcher)