Unix/Linux
Basic Linux commands
Command | Description |
ls | Lists all files and directories in the present working directory |
ls-R | Lists files in sub-directories as well |
ls-a | Lists hidden files as well |
ls-al | Lists files and directories with detailed information like permissions,size, owner, etc. |
cd or cd ~ | Navigate to HOME directory |
cd .. | Move one level up |
cd | To change to a particular directory |
cd / | Move to the root directory |
cat > filename | Creates a new file |
cat filename | Displays the file content |
cat file1 file2 > file3 | Joins two files (file1, file2) and stores the output in a new file (file3) |
mv file “new file path” | Moves the files to the new location |
mv filename new_file_name | Renames the file to a new filename |
sudo | Allows regular users to run programs with the security privileges of the superuser or root |
rm filename | Deletes a file |
man | Gives help information on a command |
history | Gives a list of all past commands typed in the current terminal session |
clear | Clears the terminal |
mkdir directoryname | Creates a new directory in the present working directory or a at the specified path |
rmdir | Deletes a directory |
mv | Renames a directory |
pr -x | Divides the file into x columns |
pr -h | Assigns a header to the file |
pr -n | Denotes the file with Line Numbers |
lp -nc , lpr c | Prints “c” copies of the File |
lp-d lp-P | Specifies name of the printer |
apt-get | Command used to install and update packages |
mail -s ‘subject’ -c ‘cc-address’ -b ‘bcc-address’ ‘to-address’ | Command to send email |
mail -s “Subject” to-address < Filename | Command to send email with attachment |
File Permission commands
Command | Description |
ls-l | to show file type and access permission |
r | read permission |
w | write permission |
x | execute permission |
-= | no permission |
Chown user | For changing the ownership of a file/directory |
Chown user:group filename | change the user as well as group for a file or directory |
Environment Variables command
Command | Description |
echo $VARIABLE | To display value of a variable |
env | Displays all environment variables |
VARIABLE_NAME= variable_value | Create a new variable |
Unset | Remove a variable |
export Variable=value | To set value of an environment variable |
User management commands of linux
Command | Description |
sudo adduser username | To add a new user |
sudo passwd -l ‘username’ | To change the password of a user |
sudo userdel -r ‘username’ | To remove a newly created user |
sudo usermod -a -G GROUPNAME USERNAME | To add a user to a group |
sudo deluser USER GROUPNAME | To remove a user from a group |
finger | Shows information of all the users logged in |
finger username | Gives information of a particular user |
Networking command
Command | Description |
SSH username@ip-address or hostname | login into a remote Linux machine using SSH |
Ping hostname=”” or =”” | To ping and Analyzing network and host connections |
dir | Display files in the current directory of a remote computer |
cd “dirname” | change directory to “dirname” on a remote computer |
put file | upload ‘file’ from local to remote computer |
get file | Download ‘file’ from remote to local computer |
quit | Logout |
Process command
Command | Description |
bg | To send a process to the background |
fg | To run a stopped process in the foreground |
top | Details on all Active Processes |
ps | Give the status of processes running for a user |
ps PID | Gives the status of a particular process |
pidof | Gives the Process ID (PID) of a process |
kill PID | Kills a process |
nice | Starts a process with a given priority |
renice | Changes priority of an already running process |
df | Gives free hard disk space on your system |
free | Gives free RAM on your system |
VI Editing Commands
Command | Description |
i | Insert at cursor (goes into insert mode) |
a | Write after cursor (goes into insert mode) |
A | Write at the end of line (goes into insert mode) |
ESC | Terminate insert mode |
u | Undo last change |
U | Undo all changes to the entire line |
o | Open a new line (goes into insert mode) |
dd | Delete line |
3dd | Delete 3 lines |
D | Delete contents of line after the cursor |
C | Delete contents of a line after the cursor and insert new text. Press ESC key to end insertion. |
dw | Delete word |
4dw | Delete 4 words |
cw | Change word |
x | Delete character at the cursor |
r | Replace character |
R | Overwrite characters from cursor onward |
s | Substitute one character under cursor continue to insert |
S | Substitute entire line and begin to insert at the beginning of the line |
~ | Change case of individual character |