Linux

Some useful commands

  • Free memory (2.2G/7.6G)
    free -h | awk '/^Mem:/ {print $3 "/" $2}'

  • Top 10 most memory intensive processes
    ps axch -o cmd:15,%mem --sort=-%mem | head

  • Top 10 most CPU intensive processes
    ps axch -o cmd:15,%cpu --sort=-%cpu | head

  • Does your Terminal Emulator support Italics?
    echo -e "\e[3m foo \e[23m"

  • dd command usage to burn an iso to a flash drive
    dd if=Downloads/archlinux-x86_64.iso of=/dev/sdb status=progress

  • Display the SSID of connected network
    nmcli -t -f active,ssid dev wifi | egrep '^yes' | cut -d\' -f2

  • Colormap in terminal
    msgcat --color=test

  • Set a random wallpaper from r/earthporn
    wget -O - -q reddit.com/r/earthporn.json | jq '.data.children[] |.data.url' | head -1 | xargs feh --bg-fill

  • Browse memes from r/memes
    wget -O - -q reddit.com/r/memes.json | jq '.data.children[] |.data.url' | xargs feh

  • Runs command1 1 out of 10 times
    [ $[$RANDOM % 10] = 0 ] && command1 || command2
    [ $[$RANDOM % 10] = 0 ] && timeout 5 command1 || command2
    [ $[$RANDOM % 10] = 0 ] && cmatrix || clear

Connect to a hidden wifi network using nmcli

nmcli c add type wifi con-name <connect name> ifname wlp1s0 ssid <SSID>
nmcli con modify <connect name> wifi-sec.key-mgmt wpa-psk
nmcli con modify <connect name> wifi-sec.psk <password>
nmcli con up <connect name>

Change MAC address using macchanger

sudo service network-manager stop
sudo ifconfig wlan0 down
sudo macchanger -r wlan0
sudo ifconfig wlan0 up
sudo service network-manager start

Desktop Entry Template

Example .desktop file (~/.local/share/applications):

[Desktop Entry]
Name=pCloud
GenericName=pCloud Client
Exec=/opt/pcloud
Terminal=false
Type=Application
Categories=Application;
Comment=pCloud Cloud Storage

Useful Programs

  • man [program] - view man pages for programs.
  • apropos - search the manual page names and descriptions.
  • [program] --help/-h
  • cat
  • tr - translate or delete characters.
  • cut - remove sections from each line of files.
    • cut -d, -f 2,3 ratings.csv - output only the 2nd and 3rd columns from ratings.csv file.
  • less
  • echo
  • head
  • date - print or set the system date and time.
    • date +%s - unix timestamp.
  • time - run programs and summarize system resource usage.
  • cal - displays a calendar.
  • cd - change working directory.
    • cd - - change to previous working directory.
    • cd ~- - same thing as cd - without echoing the path.
  • tail
  • pwd - print name of current/working directory.
  • passwd - change user password.
  • alias - list and create aliases.
  • mkdir -p folder/{sub1,sub2}/{sub1,sub2,sub3} - make directories/subdirectories quickly.
  • chsh - change login shell.
  • grep - pattern searching.
  • fdisk - disk partition utility.
  • cfdisk - disk partition utitlity.
  • dd - convert or copy a file, create bootable USBs from ISOs. use cautiously. can destroy data irreversibly. To monitor the progress of an operation, add the status=progress option to the command.
  • wc - print newline, word and byte counts for files.
  • history - show history.
    • <space>man man - don't add man man command to history.
    • fc - fix a long command that you messed up.
    • !666 - run 666th command in history.
    • !-n - refer to the command n lines back.
    • !-1 / !! - refer to the previous command.
    • sudo !! - run previous command but append sudo at the beginning.
    • [program] !! - run previous command using [program].
  • lsusb - list USB devices.
  • lsblk - list information about block devices.
  • env / printenv - list all environmental variables.
  • free - display amount of free and used memory in the system.
  • df - report file system disk space usage.
  • du - estimate file space usage.
    • du -sh dir/ - check size of dir/ on disk.
  • fc-list - list available fonts.
  • timedatectl - control the system time and date.
    • cat /etc/timezone - (on Debian) print current timezone.
  • xprop - property displayer for X.
  • shred - overwrite the specified file(s) repeatedly, in order to make it harder for even very expensive hardware probing to recover the data.
  • mount - mount a filesystem.
  • clear - clear the terminal screen.
  • locate - find files by name.
  • updatedb - creates or updates a database used by locate.
  • find - search for files in a directory hierarchy.
  • file - determine file type.

System Monitoring

  • ps - report a snapshot of the current processes.
    • ps aux | grep nginx - search for 'nginx' in ps output.
  • htop - interactive process viewer.
  • top - display Linux processes.
  • cat /proc/loadavg - load average.
  • uptime - tell how long the system has been running.
  • w - see who is logged on and what they are doing.
  • acpi - shows battery status and other ACPI information.
    • (upower -i `upower -e | grep 'BAT'`) - battery information.
  • pidof [program] - find the process ID of a running program.

System Info

  • lsb_release -a - print distribution-specific information.
  • cat /etc/*release
  • uname -a - print system information.
  • cat /etc/fstab - static file system information.

Networking

  • vim /etc/resolv.conf - change DNS server.
  • ip - show / manipulate routing, network devices, interfaces and tunnels.
    • ip addr - display IP addresses and property information.

Miscellaneous

  • Drop into a tty(tty3): Ctrl + Alt + F3
  • Move to different ttys: Alt + Left/Right
  • Mod Keys:
    • Mod1 : Left alt
    • Mod3 : Right Alt
    • Mod4 : Super/Windows
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