# Basic Commands # cd - Usage - To change directories - Examples ```bash cd temp # browses to the directory called temp cd /usr/bin # browses to /usr/bin folder cd - # browse to previous directory cd .. # browse to the parent direcotry cd ../../ #browse 2 parent directories behind ``` # pwd - Usage - To print current working directory - Examples ```bash pwd # simply lists the current folder you are in ``` # ls - Usage - To list all the files and directories - Examples ```bash ls # lists current directory ls -l # list current directory with details ls -a # list all the hidden files ls -R # list recursively ``` <p class="callout info">Please note, you can combine a number of the switches in one query rather than running them one by one. e.g. `ls -lah`</p> # mkdir - Usage - to create a new directory - Examples ```bash mkdir directory #create a folder with the name directory mkidr -p directory/data #create a folder with a subfolder called data ``` # cp - Usage - Copy a file from one place to another - Examples ```bash cp hash /temp #copies file into the specified folder cp hash hash1 #copies the content of a file into a different one cp -r folder1/ folder2/ #copies the folder with it's content into a folder called folder2 ``` # mv - Usage - To move a file from one place to another, also can be used to rename a file. - Examples ```bash mv file1 ../ #moves the file from the current folder to the parent folder mv file1 file2 #renames file1 to file2 ``` # touch - Usage - To create an empty file. - Examples ```bash touch file1 #create file 1 touch hash && echo "some_text" > hash # create a file cat hash and write in the file the words "some_text" ``` # cat/tac - Usage - To read the content of a file. - Examples ```bash cat hash # read the content of the file called hash tac hash # same as above ``` # rm - Usage To remove a file or folder. - Examples ```bash rm file1 # remove file1 rm -rf folder1 # recursively remove the content of folder1 and discard any files in use. ``` # grep - Usage Search for a line or specific text in a file. - Examples ```bash grep "text" file_with_text.txt # Print all lines that have the word "text" grep -c "text" file_with_text.txt # Count the number of occurences of the word "text" grep -i "text" file_with_text #Print all lines that contain the case insensitive word "text" ```

The grep function has a ton of use cases, it can do regex matches, show lines before or after specific text and a lot more. I would advise to read the manual pages for more use cases. See the below URL for more information on the command: [GNU Grep 3.7](https://www.gnu.org/software/grep/manual/grep.html)

# head - Usage - Read the first n lines of a file. - Examples ```bash head file.txt # Default behaviour is to output the first 10 lines of a file head -n 3 # Output the first 3 lines of a file ``` # tail - Usage - Read the last n lines of a file - Examples ```bash tail file.txt # Default behaviour, output the last 10 lines of a file tail -n 3 # Output the last 3 lines of a file ``` # chmod - Usage - To change the permissions of a file or folder - Examples ```bash chmod +x file1 # make a specific file executable chmod 754 file1 # grant the file read, write, execute to user, read and execute to group and read to other ``` # echo - Usage - To write something in the console or file. - Examples ```bash echo "Some really interesting text" #write the test between brackets ``` # clear - Usage - To clear the terminal windows of text. - Examples ```bash clear # clears the terminal window ``` # sudo - Usage - To escalate your privileges to super user. - Examples ```bash sudo ./script.sh # execute the script as root sudo apt install memes # escalate your privileges to install the application called memes ```