File and Directory Management:

ls:

Purpose: Lists directory contents.
Example: ls -la (shows details, including hidden files).
```
   ls -la
```

cd:

Purpose: Changes current directory.
Example: cd directoryname.
```
  cd dir2
```

pd:

Purpose: Prints current directory path.
Example : pwd.
output: /home/user
```
  pwd
```

mkdir:

Purpose: Creates a new directory.
Example: mkdir directory_name.
```
  mkdir directory_name
```

r/rmdir :

Purpose: Deletes files or directories.

Examples:

rm-rf :- Forcefully removes even non empty files and directory.
rm-rp :- Removes non empty directory including parent and sub directory.
rm-r :- Removes empty directory.
rm-rf*:- Removes all directory & files except hidden files.
rmdir :- Removes the specified directory.
rmdir-p :- Remove parent & child directory.
rmdir-pv :- Remove all parent & sub directories along with verbose.
```
  rmdir directory_name
```

cp:

Purpose: Copies files or directories.
Example : cp file_name (Source) file_name (destination).

Data of file1 will be overwritten to file2.
```
  cp file1 file2
```

mv:

Purpose: Moves files into directories or renames files.

Note: Directory can also be move to directory but file can’t move to file.

Examples:

mv File_name (Source) Directory_name(Destination). {used to move file to directory}
mv File_name (oldname) File_name(Newname). {used to rename file or directory}
```
  mv File1 Dir1
  mv File1 Myfile
```

touch:

Purpose: Creates a single or many empty File and used to change timestamp of a file or update any one type of time of a file.

Example : touch file_name

Time Stamp: Every file has three types of time associated with it.

Access time:- Last time when a file was accessed.

Example : touch-a (it will change access time to current time)
Modify time:- Last time when a file was modified.

Example : touch -m (it will change modify time to current time)
Change time:- Last time when file meta data was changed.

Example : touch -c (it will change change time to current time)
```
  touch file1
  touch -a
  touch -m
  touch -c
```

File Viewing and Editing:

cat:

Purpose: Creates Single File , Combine two or more files to make one , To add new content in same file , To display file content.

Example :

cat > file_name {used to create file}
cat file_name {used to show content inside file}
cat file1_name file2_name » file3_name {Data of file1 & file2 will be combined and data will be shown into file3}

cat » file_name { since content can’t be edit but new content can be added}

  cat > file1
  cat file1
  cat file1 file2 » file3
  cat » file1

less:

Purpose: Views files page by page.
Example: less file_name.
```
  less file1
```

Purpose: Views files (simpler than less).
Example: more file_name.
```
  more file1
```

nano:

Purpose: Edits text files (beginner-friendly).
Example: nano file_name (Ctrl+O → Ctrl+X → Y to exit).
```
   nano file1
```

vim:

Purpose: Edits text files (advanced).
Example: vim file_name(i to edit, :wq to save/quit).
```
  vim file1
```

head:

Purpose: Shows first 10 lines of a file.
Example: head file_name (first 10 lines).
```
  head file1
```

tail:

Purpose: Shows last 10 lines of a file.
Example: tail file_name(last 10 lines).
```
  tail file1
```

Permissions and Ownership

chmod:

Purpose: Modifies file/directory permissions.
Example: chmod 777 directory_name.

chown:

Purpose: Changes file/directory ownership.
Example: chown username file_name/directory_name.

chgrp:

Purpose: Changes file/directory group.
Example: chgrp groupname file_name/directory_name

ls -l:

Purpose: Displays permissions and details.

Example: ls -l.

  chmod 777 dir1
  chown username file1
  chgrp groupname file

Networking:

ping:

Purpose: Tests network connectivity.
Example: ping google.com.

curl:

Purpose: Fetches data from URLs.
Example: curl https://example.com.

wget:

Purpose: Downloads files from the web.
Example: wget <url>.

ifconfig:

Purpose: Shows same as windows ip config tells us ip & ethernet and Nid of our machine.
Example: ifconfig.

ip:

Purpose: Manages network settings (modern).

Example: ip addr (shows IP addresses).

  ping google.com.
  curl https://example.com
  wget https://example.com/file.txt
  ifconfig
  ip addr

Task: What is the linux command to

To view what's written in a file.

cat – View Entire File.
```
  cat filename
```

To change the access permissions of files.

chmod - change mode.
```
  chmod mode filename
```
mode: can be numeric (755) or symbolic (u+rwx).
filename is the file or directory whose permissions you want to change.

To check which commands you have run till now.

history :- This will display a numbered list of all previously executed commands.

history

To remove a directory/ Folder.

Use the rmdir command if the directory is empty.
Use the rm-r command.
```
  rmdir myfolder
  rm -r dir1
```

To create a fruits.txt file and to view the content.

Using touch.
Using cat.
Using vim/vi .

Using nano.

  touch fruits.txt
  cat > fruits.txt
  vim fruits.txt
  nano fruits.txt

  # To view :
  cat fruits.txt

Add content in devops.txt (One in each line) - Apple, Mango, Banana, Cherry, Kiwi, Orange, Guava.

Using echo with \n.

Using cat.

  echo -e "Apple\nMango\nBanana\nCherry\nKiwi\nOrange\nGuava" > devops.txt
  cat >> devops.txt
  # now editor will open after cat command and we'll put manually 
  Apple
  Mango
  Banana
  Cherry
  Kiwi
  Orange
  Guava

To Show only top three fruits from the file.

head command will be used.
```
  head -n 3 devops.txt
```

To Show only bottom three fruits from the file.

tail command will be used.
```
  tail -n 3 devops.txt
```

To create another file Colors.txt and to view the content.

Using touch.
Using cat.
Using vim/vi .