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).
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)”
The 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 “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 “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
The 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.
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.
1. "mv" to move file or folder
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.
2. “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.
The 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
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).
Used to display each line of the file starting from the first row and finishing on its last row.
Syntax: cat file_name
The command “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
The command “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 “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 “ls” displays the list of all directories, folder, and files present in the current directory.
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.