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touch used to create a new files like text files , media files.
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cd used to change a directory/folder.
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ls used to list all the files of a directory.
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ls -l used to list files in long list format.
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-m used to modifying a access time of file (eg. touch -m old.txt).
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file used to check type of a file.
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sudo apt update used to update package (advanced packaging tool).
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rm used to remove files.
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rm -i used to prevent files from accidently deletion by confirming before deletion.
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rm -rf used to everything from directory.
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cp used to copy a file.
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mv used to moving or renaming a file.
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head used to show specific content from a file from starting.
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tail used to show specific content from a file from end. (Eg. tail -15 /dir1).
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cat used to view and modifying a content of file. (Eg. cat file.txt or cat > file2.txt (for modifying)).
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ls -la used to list all the files including hidden files.
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pwd used to determined the location of currently working directory.
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cd ~ used to go to the home directory.
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cd.. used to go one directory back.
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echo used to print
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echo 'data' >> filename used to add content in a file
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clear used to clear the screen.
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append (>) used to append content to a file .
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append (>>) used to append content to a file without overwriting.
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grep used to search particular patterns in a file (i.e. filter).
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pile (|) used to join two command.
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ps This command shows all the running processes.
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kill used to kill the process using process id (PID).
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NOTE: you can use -9 to forcefully kill the app e.g kill -9 122.
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Ctrl + C used to cancel the currently running command.
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Ctrl +A move the cursor at the beginning of line.
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Ctrl +B move the cursor backward one character.
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Ctrl +E moves the cursor end of the line.
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Ctrl + P pastes previous lines.
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Ctrl + W delete the last word typed.
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Ctrl + U delete the complete line.
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Ctrl + R used for searching previously used commands.
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Ctrl + S stops all output on screen.
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; used to operate more than one command in a line.
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& (ampersand ) used to run command in a background.
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&& works as a logical AND (i.e run commands only if both command are correct otherwise shows error).
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# used to comment**
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history list all the commands used by the user.
- vi used to create new file (ie vi filename) [Note: use Esc key then press ":wq" to save file and exit editor].
- vi -R filename used open file in read-only mode.
- view filename used to view file.
- sleep used to suspend execution for a specific number of seconds.
- cal used to show calendar.
- date used to show date.
- time used to summarize the execution time of a command.
- A shell file is created with .sh extension (i.e. vim myscript.sh).
- add #! /bin/bash at the starting .
- To run script use sh file.sh command.
- /etc/passswd contains the information about user account and their passwords.
- /etc/shadow contains the information about user passwords in encrypted form.
- /etc/group contains the information about groupss.
- /etc/gshadow contains the information about secure group.
- r read -- denoted with 4
- w write -- denoted with 2
- x execute -- denoted with 1
- chmod used to change permission [e.g chmod u+rw file.txt ]
NOTE: strings command is used to read binary files e.g strings /bin/pwd