Getting familiar with terminal 2

In this tutorial, we will assume that you are already familiar with the basics of Linux. If not, please review the basics: link.

We will cover some shortcuts, commands, file permissions, and the super user account in this tutorial.

Shortcuts

riza@hussain:~/projects$ ls . # we use dot `.` for current directory 
 macro  'main.mojo ' # output

riza@hussain:~/projects$ cd .. # we use .. for previous directory
riza@hussain:~$

riza@hussain:~$ cd - # we use - for previous working directory(previous working)
/home/riza/projects

riza@hussain:~/projects$ echo "hello" > hello.txt
# we use > operator for redirecting output
# similarly we use < operator for redirecting input 
# this operation creates a file named hello.txt and writes in "hello" (overide)

riza@hussain:~/projects$ echo "hello" >> hello.txt
# we use >> operator to append output of echo to hello.txt

riza@hussain:~/projects$ cat 'main.mojo ' #we use cat operator to display file content
from sys import argv      
fn main():
    let li = argv():
    print_no_newline(li," ")
    print()

rm command

riza@hussain:~/projects$ ls
 hello.txt   macro  'main.mojo '
riza@hussain:~/projects$ rm hello.txt # we use rm command to remove files
riza@hussain:~/projects$ ls
 macro  'main.mojo '

riza@hussain:~/projects$ rm -r *   # we use rm -r to recursively remove all files (*)
riza@hussain:~/projects$ ls

File permissions

many times user struggle with this concept in unix. I’ll try to keep it simple

#use ls -l to list all the files in long form 
riza@hussain:~/projects$ ls -l
total 4
-rw-r--r-- 1 riza riza 0 Oct 22 22:02 echo
-rw-r--r-- 1 riza riza 6 Oct 22 22:03 hello.txt

now whats `-rw-r--r- -r- -` its actually mainly three permission for three users. first three are for user u, second three are for group gand last three are for others o. Here r stand for read, w stands for write and x stands for executable. Here in above we see that all the files above are not executable. To change file permission we use chmod [ugo][+-][rwx] file name will make a file executable. let us see some examples

riza@hussain:~/projects$ chmod u+x hello.txt #here we use u for user x to make executable + to add 
riza@hussain:~/projects$ ls -l
total 4
-rw-r--r-- 1 riza riza 0 Oct 22 22:02 echo
-rwxr--r-- 1 riza riza 6 Oct 22 22:03 hello.txt
# here above you see a x has been placed 
# now to make this file again not executable we use - instead of +

riza@hussain:~/projects$ chmod u-x hello.txt
riza@hussain:~/projects$ ls -l
total 4
-rw-r--r-- 1 riza riza 0 Oct 22 22:02 echo
-rw-r--r-- 1 riza riza 6 Oct 22 22:03 hello.txt

riza@hussain:~/projects$ chmod g+x hello.txt #here we use g for group
riza@hussain:~/projects$ ls -l
total 4
-rw-r--r-- 1 riza riza 0 Oct 22 22:02 echo
-rw-r-xr-- 1 riza riza 6 Oct 22 22:03 hello.txt

Lets go to the root

In unix installing many packages requires root privilages.To use this we use sudo (do as super user)

riza@hussain:~$ cd /bin
riza@hussain:/bin$ touch hello
touch: cannot touch 'hello': Permission denied
riza@hussain:/bin$ sudo touch hello #it works

To remain continous as super user we use sudo su

riza@hussain:/bin$ cd ~
riza@hussain:~$ sudo su
root@hussain:/home/riza# #changes to root user from riza@hussian to root@hussain

That’s all for this tutorial on Linux basics. Next, we will learn about shell scripting. In the meantime, keep practicing using the Linux shell!