essentials

In this section, I will be discussing some basic Linux commands, along with a few basic flags associated with each commands. The term flag refers to the arguments/parameters supplied to the command.

apt, apt-get, file, diff

ls

Lists contents in specified directory. If <dir> value is omitted, the current directory would be used instead

$ ls <dir>
Desktop Downloads Documents 
Public Pictures ...

Useful flags

-l

To display content in long listing format

$ ls -l 

-a, --all

To display all content including those starting with . (hidden files)

$ ls -a 

Combination of multiple flags

• Display all content including hidden files (starting with .), in long listing format

$ ls -la 

pwd

To print the current working directory

user@linux:~/$ pwd
/home/user

cd

To change directory

$ cd <dir>

Basic example

# print the current working directory
user@linux:~/$ pwd
/home/user

# change directory
user@linux:~/$ cd test_dir

# pwd displays the updated directory
user@linux:~/test_dir$ pwd
/home/user/test_dir

mkdir

To create a new directory

$ mkdir <new_dir>

# example
user@linux:~/$ mkdir test_dir
user@linux:~/$ cd test_dir
user@linux:~/test_dir$ 

cat

From manpage: "concatenate files and print on standard output". In simple terms, it displays the content of a particular input file

$ cat test_file.txt
here is a test file
next line here

Useful flags

-n, --number

To display output line numbers

$ cat -n test_file.txt
1 here is a test file
2 next line here

$ cat ---number test_file.txt
1 here is a test file
2 next line here