Forem: Sivakumar

Your Guide to Basic Linux Commands Day07

Sivakumar — Sat, 21 Jun 2025 11:26:02 +0000

xargs

xargs is a command-line utility in Unix/Linux used to build and execute command lines from standard input. It's often used to convert output from one command into arguments for another command.

It can also be used for other purposes with its switches like:

xargs -a = will show the contents of a file

Example:

echo f1 > file01.txt | xargs rm
xargs -a file02.txt

runlevel

Modern Linux distros use a concept called targets from systemd. runlevel is a concept of system initialization from the sysV . This defines the mode of operation whether its in single user mode , multi user mode , etc...
The different run levels are :
0 Halt (shuts down the system)
1 Single-user mode (for maintenance)
2 Multi-user mode (no network)
3 Multi-user with networking (text mode)
4 Undefined / user-definable
5 Multi-user with GUI (graphical desktop)
6 Reboot
Example:
runlevel

init

init is the first command that will run when the system starts. It will always have the process id 01 and starts other process. This command can be used to switch between different run levels.

Example:

init 0
init6

The "init 0" command will shutdown the system and "init 6" will reboot the system.

ps

This command will display a snapshot of the current active processes in the system.This has quite a few switches like:

ps -x - displays process run by the user
ps -ax - displays all the process using BSD syntax

Example:

ps
ps -x

pstree

This command will display a tree structure of the processes running. It is very helpful to identify which process started others and debug.

Example:

pstree
pstree -p saber ##displays the user process

Your Guide to Basic Linux Commands Day06

Sivakumar — Fri, 20 Jun 2025 17:21:31 +0000

grep

The grep is used to identify patterns in a file and show the lines that match the pattern. This also includes its switches:

grep -v = shows the lines that does not match the pattern
grep -i = searches through the file with case insensitive

Examples:

grep "is" file01.txt
grep -i "error" logfile.txt

wc

The wc or word count command displays the number of lines, words
, letters in the given file. It's switches consist of:

wc -m = prints the character counts
wc -l = prints the number of lines

Examples:

wc linuxfile.txt
wc -m linuxfile.txt

sort

The sort filter can be used to show the output in a sorted order in the terminal. It will not actually sort the order within the file. Sort has so many switches but few of them are:

sort -f = is case insensitive when it comes to sorting
sort -n = compare and sort according to numerical value

Example:

sort file01.txt
sort -f file01.txt

uniq

The uniq command displays only the unique contents within the file. It has quite a few switches namely:

uniq -c = prints the count of occurrence of a word
uniq -i = ignores the case sensitive

Example:

cat file01.txt | uniq
sort file01.txt | uniq -c

whoami

This command displays the current user of the system.

Example:
whoami

Your Guide to Basic Linux Commands Day05

Sivakumar — Thu, 19 Jun 2025 16:55:38 +0000

echo

The echo command will display each argument it receives from the shell. The echo command will also add a new white space between the arguments it received.
Example: echo hello world

type

Not all the commands available in linux are internal builtin commands. There are commands that are saved in a separate location known as external command. To identify whether a given command is builtin or external command, you can use the type command.
Example:

type ls
type cd

history

This command allows you to see the shell command history has been executed so far.
Example:
history

cut

The cut command will allow you to see the selected columns in a file.
Example:
cut -d: -f1,3 /etc/passwd | tail -4

tr

The tr(translate) command will replace the occurrence of a given character with another argument give.
Example:
cat file01.txt | tr 'e' 'E'

Your Guide to Basic Linux Commands Day04

Sivakumar — Wed, 18 Jun 2025 09:34:30 +0000

cat

Today We are going to take a look at the cat command and its types.It's a universal command and can be used in many ways.In the first example , you can use it to display the contents of a file.
Example:
cat file01.txt

concatenate

You can also use cat to concatenate multiple files into a single bigger file.Try the commands below one by one
Example:

echo one > part1
echo two > part2
echo three > part3
cat part1 part2 part3
cat all

Here the echo command returns the input given that is one and this command is saved in part 1 file and the same for part2 and part3. This is then concatenated together using cat command and displayed using cat all

Createfiles

The cat command can also be used to create a file and allows you to write until you use ctrl+d which will send an EOF(End Of File) command and save the file.

Example:
cat > file86.txt

Copyfiles

The same cat command can also be used to copy a file.

Example:
cat file86.txt > file95.txt

tac

This is the reverse of the cat display command which will display the contents of the file in reverse order.
Example:
tac file86.txt

Wrapping up

This will be all the commands for today.We will be going more into arguements and control operators next time. Have fun learning

Your Guide to Basic Linux Commands Day03

Sivakumar — Tue, 17 Jun 2025 15:51:10 +0000

cp

This command allows you to copy one file content to another file in the terminal. you can even copy directories in the same method which copies all the source files.

This command also has multiple switches like:
cp -r = this allows you to even copy the subdirectories using recursive option.
cp -i = this switch asks you with a yes/no if there already exists a file with some content that is about to be rewritten by copying

example :
cp file01.txt fileo2.txt
cp -r dir01 dir02
cp -i file01.txt file02.txt

mv

To rename a file or move it to another location , you can use this mv command.you can also use this command to rename directories as well.

This command has a single switch -i that asks a yes/no before overwriting a file.

example:
mv -i demo.txt file01.txt

Working with file contents

The following commands we are going to take a look at will cover about performing actions on a file like reading, modifying, etc..

head

head command will show the first 10 lines of a file. You can also provide it with a n number to show that n number of lines of a line or -cn will show n number of bytes.

example:
head file01.txt
head -15 file01.txt
head -c15 file01.txt

tail

This command is very similar to that of the head command and will show the last ten lines of a file. This command has also the same switches.

example:
tail file86.txt
tail -15 file86.txt
tail -c15 file86.txt

Wrapping up

These are the commands I learned today. I will share about the cat command in the next blog since it contains so many different functions and variations

Your Guide to Basic Linux Commands Day02

Sivakumar — Mon, 16 Jun 2025 12:10:29 +0000

mkdir

Following the previous day commands on working with directories , The next command will be about how you can create a directory or a folder for yourself in the terminal. i.e mkdir
eg: mkdir newdirectory

There is a switch available for this command that allows you to create multiple directories within another directory by using mkdir -p
eg:mkdir -p mydir2/mysubdir2

rmdir

This command allows you to delete a directory when it is empty.otherwise it will show that the directory cannot be deleted.
eg:rmdir newdirectory

This also has the same switch that allows you to delete the parent directories recursively.
eg:rmdir -p mydir2/mysubdir2

File Management Commands

These commands allow you to create, modify , delete files.All the files are case sensitive and therefore treated as different files.

file

The file command shows the datatype of a file.Linux does not use extensions to determine the type of a file.The file command uses a magic file(literally it's name) that contains patterns to recognise file types.file is located in /usr/share/file/magic.
eg:file file54.pdf , file /etc/passwd

touch

The touch command allows you to create an empty file.
eg: touch file86.txt
Like other commands , This command also has multiple switches available like:

touch -t = allows you to set the time on when the file was created. eg: touch -t 2412311159 demo.txt

rm

This command removes a file forever since it will not be sent to trash or recycle bin.
eg:rm file86.txt

The switches available for this commands are:

rm -i = using this switch prevents accidental deletion of a file by asking for confirmation before deleting the file.
rm -rf = This switch recursively deletes the file forcefully. It can even delete everything if not used in the proper environment. So be careful when you use it.

Wrapping up

This will be the commands for today. Try experimenting on them to your preferences and also refer to man pages if you want to learn a lot more.

Your Guide to Basic Linux Commands Day01

Sivakumar — Sun, 15 Jun 2025 11:41:58 +0000

  Sometimes , It is really confusing on where to begin with Linux and its commands in general. Today I am going to share how I begin my journey .

man

  The simplest command you can start from is by using man command where **man** refers to manual . This command can show the definitions , types or switches of other commands , files etc.

eg: man man , man ls

pwd

   The next command that will help you with your everyday activity will be the **pwd** command. This command shows you the current working directory or where you are working in the terminal.

eg: pwd

ls

   This command is one of the easiest yet satisfying command . i.e **ls** , It will show all the files that is the directory or folder you are currently in.

eg:ls
Here we will introduce the concept of switches(-), This will allow you to modify the base command into other predefined choices to show other outputs. Such switches for the ls commands are

ls -a= allows you to see hidden files in the directory.
ls -l= shows the files in long listing order.
ls -lh= -h switch in general shows contents in human readable format. Using it with -l(or -lh)shows long listing in readable format.

cd

   The following command will be your primary way of navigating forward and backward from the linux terminal. In Linux , Everything is considered as a file and you can find anything in the format as a file hiding somewhere in some directories you cannot figure out.

  There are two concepts in navigating through all these files. Absolute path and relative path. When you type a path

starting with a slash (/), then the root of the file tree is assumed. If you don't start your path with a slash, then the current directory is the assumed as the starting point.eg: /home/Documents(absolute path), New_Folder/Images(Relative path)

   Therefore by using the **cd** command , you can go to the path we mentioned above and access the files in those directories.

eg:cd Documents
The other types for the cd commands are

cd -~ = This is a shortcut to get you back to your home directory
cd .. = This takes you back to your parent directory or one folder back step.
cd - = This allows you to go back to the previous directory where you were working on

Wrapping Up

These Commands are pretty easy to implement and some of them will work regardless whether it is windows or linux(no experience with mac unfortunately).

Try the man command for these commands since there are so many switches for all these commands and so much to learn. So, try working them out on your own :)