Linux/Ubuntu Commands

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  1. Use lshw (list hardware) to show the computer hardware information.

  2. Use uanme -a to show system information.

  3. tar

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    tar –xvf file.tar # unzip .tar
    tar -xzvf file.tar.gz # unzip .gz
    tar -xjvf file.tar.bz2 # unzip .bz2
    tar –xZvf file.tar.Z # unzip .Z
    unrar e file.rar # unzip .rar
    unzip file.zip # unzip .zip

  4. Show the structure of current directory.

    1. sudo apt install tree
    2. tree -L N show \(N^{th}\) depth.

  5. #!/bin/bash indicates the path to shell. It can only be placed at the top of shell script and begun with #!.

    1. #! is known as shebang in Unix.
    2. This command is used to instruct our system to use bash as default shell.

  6. vim :set number to show the line number.

  7. vim comment out a block (in a shell script #)

    1. :10,20s/^/#/g to comment out a block from line 10 to 20
    2. :10,20s/#//g to delete the comments.

  8. vim delete a line: click the line->exit Insert mode->double press d in your keyboard

  9. How to calculate the time consumption of a shell script. Here is an example. Pay attention to the spaces in this script.

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    #!/bin/bash
    startTime=`date +%s`
    for ((i=1; i<=100; i++)); do
            a=$[$i%20]
            if [ $a -eq 0 ]; then
                    echo "i: $i"
            fi
    done
    endTime=`date +%s`
    consumedTime=$[ $endTime - $startTime ]
    echo "Time consumed: $consumedTime seconds"

  10. How to show the folder size in terminal. du: summarize disk usage of the set of files, recursively for directories.

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    $ du -sh # show the size of current folder
    $ du -h # show the sizes of all subfolders/files (recurssively)
    $ du -h <folder name> # show the sizes of indicated folder/files

  11. find .|xargs grep -ri "characters you want to find" search all files under current directory to find specific characters.

  12. The default editor in Ubuntu is GNU nano. You may dislike it, so please use vim in default.

    1. sudo update-alternatives --config editor
    2. choose vim.basic
    3. source ~/.bashrc

  13. If you cannot type in terminal, you may happen to press CTRL+S which locks screen. Just press CTRL+Q to exit.