Commands used for System Information
The simple “date” command displays the current date and time (including the day of the week, month, time, time zone, year).
default, “date” command uses the time zone defined in path
“/etc/localtime”. Linux user can change the time zone via Terminal by
using command “TZ”.
Syntax: TZ=Name_of_Time_Zone date
Linux allows its user to set the current date and time of the system manually.
Syntax: date –set=”Date_in_format(YYMMDD) Time_in_format(HH:MM)”
To operate the system on a specific date, you can change the date by using “-d”.
Syntax: date -d Date_to_operate_system_on
date -d now
date -d yesterday
date -d tomorrow
date -d last-Sunday
date -d “1997-04-22”
command “df” shows the amount of disk space used and disk space
available on every file system containing each filesystem’s name and its
a. df -h
command “df -h” shows the same result as the command “df” but now the
data is in a more human-readable form which can be easily comprehended
by a new user.
Syntax: df -h
The command “free” displays the amount of free and used memory in the complete system.
The command “ps” which is also known as process status command is
used to provide information about the processes currently running on
the system, including their respective process identification
command “uptime” provides information about how long the system has
been running in one line. Result for this command includes the current
time, the time duration system has been running for, the number of users
who are currently logged on, and the system load averages for the past
1, 5, and 15 minutes respectively.
The command “w” displays the detailed information about the users who are logged in the system currently.
The command “passwd” stands for password and it is used to change the password of the user.
Syntax: passwd user_name
The command “exit” as the name says it is used to exit from the system and log out from the current user.
The command “shutdown” is used to shut down the system.
Commands used for File Handling
command “mkdir” allows users to create directories/folders in the
system. The user running this command must have suitable rights over the
parent directory to create a directory or they will receive an error.
Syntax: mkdir New_Directory’s_Name
Entering the command “mkdir NewDirectory” will create the directory named as NewDirectory in the current directory.
command “rmdir” allows users to remove directories/folders from the
system. The user running this command must have suitable rights over the
parent directory to remove a directory or they will receive an error.
Syntax: rmdir Directory’s_Name
Entering the command “rmdir NewDirectory” will remove the directory named as NewDirectory in the current directory.
The command “rm” is used to remove files from the directory.
Syntax: rm file’s_name
This above-mentioned command will remove the file “Test_File” from the Desktop directory.
The command “mv” is used for two purposes
- To move files or directories from one path to another path in the system.
- To rename a file or folder.
a. “mv” to Move Files
Syntax: mv Source_File_name Destination_File_Name
Consider having two files in a directory (File1 and File2). Entering the command “mv File1 File2” will move data of File1 to File2 and delete source file(i.e. File1) from the system.
b. “mv” to Rename Files
Syntax: mv File_name New_name_for_file
Consider having two files in a directory (File1 and File2). Entering the command “mv File1 File_Rename” will rename File1 to File_Rename in the same directory.
command “cp” is used to copy data from a source file to the destination
file. Its function is almost like the command “mv”. The only difference
is by using the command “cp” the source file is not removed from the
directory after its data is moved to the destination file.
Syntax: cp source_file_name destination_file_name
cp A B
Consider having two files (A and B) in Desktop Directory. Entering the command “cp A B” will copy all the data from file A to file B and user can still access both files (A and B).
The command “cat” is a reverse of the command “tac”. It is used to display each line of the file starting from the first row and finishing on its last row.
This command is more frequently used than “tac”.
Syntax: cat file_name
Consider having a file named Test_File as shown below, “cat” command will display its data on the screen.
cat File1 File2
Consider having two files (File1 and File2) in the Desktop directory. Via above-mentioned cat command, the User can display data from both the files on their screen.
cat File1 File2 >File_Output
Consider having two files (File1 and File2) in the Desktop directory. Via above-mentioned cat command the user can create a new file (File_Output) and append data from both the files (File1 and File2) into this new file named as File_Output by using operand “>”.
“head” prints the top N rows of data of the given input or file. By
default, it prints the first 10 lines of the specified files.
- head -n File_name
head -5 New_Test.txt
The above-mentioned command will only print first 5 rows of the file New_Test.txt
“tail” prints the last N rows of data of the given input or file. By
default, it prints the last 10 lines of the specified files.
- tail -n File_name
tail -5 New_Test.txt
The above-mentioned command will only print last 5 rows of the file New_Test.txt.
The command “echo” used to display any expression that is passed as an argument.
This command displays the expression “user” on the screen.
The command “grep” is used to search for a text in the specified file/folder.
Syntax: grep “expression_to_be_Searched” file_name_to_search_in
grep “Are” B
The above-mentioned command will search for the word “Are” in the text of the file B.
The command “zip” is used to compress one or more files and store them in a new file with .zip extension.
Syntax: zip new_zip_file_name.zip
zip Files.zip Check.txt Test.txt Output.txt
The above-mentioned command will compress all three files (Check.txt, and Test.txt and Output.txt) and store these in a new file which we’re creating through this command i.e. Files.zip.
The command “unzip” is used to decompress a .zip file and extract all the files within to current directory.
Syntax: unzip zip_file_name.zip
Consider having a zip File named as Files.zip with a compressed .txt file in it. The above-mentioned command will help you unzip the file (Files.zip) and extract the .txt file from it to the current directory.
The command “sudo -I” is used to continue the session as a root user which has a lot more privileges than normal system user.
Syntax: sudo -i
The simple command “history” displays the list of all commands entered since the user started the session.
Note: To clear all the previous history use command “history -c”.
The command of “help” provides you help to learn about all the built-in commands.
The command of “man” stands for manual and it is used to display the user manual of any built-in Linux command.
Syntax: man command_name
This command displays the user manual of the built-in Linux command “vim”.
The command “dir” stands for directory and it is used to display the list of all directories or folder in the current directory.
The command “ls” displays the list of all directories, folder, and files present in the current directory.
- Ls -ltr
The above-mentioned command displays the name of directories, folders, and files
The above-mentioned command displays the name of directories, folders, files with their respective owner name, group’s name and rights your user have over these.
The command “cd” stands for change directory and it is used to change the current directory user is operating in via Terminal.
- cd destination_directory’s_name (to move forward from your current directory to the next directory within current directory)
- cd .. (to move back in the previous directory from your current directory)
This command takes you from Directory /home/user to the destination directory which is /home/user/Desktop.
Note: You cannot only use cd when the destination directory is within your current directory.
This command takes you from directory /home/user/Desktop back to /home/user.
The command “pwd” displays the path of the current directory user is operating in via Terminal.
The command “clear” is to clear the screen of Terminal.
The command “whereis” is self-explanatory, as it displays the path where the package for specific built-in Linux command locates.
Syntax: whereis command_name
“whatis” is also self-explanatory, as it displays a brief description
of what is the functionality of specific built-in Linux command.
Syntax: whatis command_name
With this, we wish you all the luck for your journey with Ubuntu! You will find the OS difficult initially, however with the commands and instructions given above, you will save a lot of time. A strong grip over the Linux Terminal is what makes the user dominant over the system.February 28, 2019