Apps

system info

command description
htop activity monitor (sieht besser aus als top)
hardinfo hardware info
ncdu like du -sh, but more convenient (because avoids typing)

ffmpeg

command description
ffmpeg -i foo.mp4 bar.mp3 mp42mp3: convert foo.mp4 to bar.mp3
ffmpeg -i input.webm -c:v libx264 -preset slow -crf 22 -c:a aac -b:a 128k output.mp4 webm2mp4: convert input.webm to output.mp4
ffmpeg -i source.mp4 -ss 00:00:00 -t 00:00:00 -vcodec copy -acodec copy outsplice.mp4 crop source.mp4 from start time -ss to time -t
ffmpeg -i input.mov -qscale 0 output.mp4 mov2mp4: convert input.mov to output.mp4
ffmpeg -i input.mp4 -ss 00:05:20 -t 00:10:00 -c:v copy -c:a copy output1.mp4 take the input video input.mp4, and cut out 10 minutes from it starting from 00:05:20 (5 minutes and 20 second mark), i.e. the output video will be from 00:05:20 to 00:15:20. If you specify a duration that will result in a stop time that is beyond the length of the input video, the output video will end where the input video ends. source
ffmpeg -i input.mp4 -ss 00:05:10 -to 00:15:30 -c:v copy -c:a copy output2.mp4 uses -to to specify an exact time to cut to from the starting position. The cut video will be from 00:05:10 to 00:15:30, resulting in a 10 minutes and 20 seconds video. If you specify a time -to that is longer than the input video, e.g. -to 00:35:00 when the input video is 20 minutes long, the cut video will end where the input video ends. If you specify a -to that is smaller than -ss, then the command won’t run. You’ll get the following error: Error: -to value smaller than -ss; aborting. source
ffmpeg -i animated.gif -movflags faststart -pix_fmt yuv420p -vf "scale=trunc(iw/2)*2:trunc(ih/2)*2" video.mp4 gif2mp4: convert animated.gif to video.mp4
ffmpeg -i input.mp4 -ss 00:00:30 -t 00:00:50 -q:a 0 -map a output.mp3 mp42mp3: extract audio
ffmpeg -i input.mp4 -vcodec libx265 -crf 28 output.mp4 push the compression lever further by increasing the CRF value — add, say, 4 or 6, since a reasonable range for H.265 may be 24 to 30. Note that lower CRF values correspond to higher bitrates, and hence produce higher quality videos., unix.stackexchange

vlc

command description
vlc -L -- "-some-filename-that-starts-with-a-dash.mp4" loop a video

convert (imagemagick)

command description
sudo apt install imagemagick image editing, converting, compressing, etc.
convert path/to/image.png -resize 640x path/to/output_image.png compress an image.png by resizing / scaling down (source)
convert path/to/image.png -quality 50% path/to/output_image.png compress an image.png by reducing its quality (source)
convert *.PNG mydoc.pdf create a pdf from all .PNG files in the current folder; important: must run sudo mv /etc/ImageMagick-6/policy.xml /etc/ImageMagick-6/policy.xmlout first to fix convert-im6.q16: attempt to perform an operation not allowed by the security policy PDF' @ error/constitute.c/IsCoderAuthorized/413. error, askubuntu
convert EXAMPLE.png EXAMPLE.svg convert png to svg

pdftoppm (poppler)

command description
sudo apt install poppler-utils install pdftoppm
pdftoppm -png myfile.pdf > myfile.png convert single page PDF with poppler
pdftoppm -png myfile.pdf myfile converts multipage PDF with poppler
pdftoppm -jpeg myfile.pdf > myfile.jpg convert pdf to jpeg

pdftk

  • crop pdf, extract pdf pages, cut pdf
  • merge pdfs
  • add pdf toc
command description
sudo apt install pdftk  
sudo snap install pdftk  
pdftk full-pdf.pdf cat 12-15 output outfile_p12-15.pdf to save pages 12-15 from full-pdf.pdf in outfile_p12-15.pdf
pdftk mt01.pdf mt02.pdf mt03.pdf mt04.pdf mt05.pdf mt06.pdf mt07.pdf mt08.pdf mt09.pdf mt10.pdf mt11.pdf mt12.pdf mt13.pdf mt14.pdf mt15.pdf mt16.pdf mt17.pdf mt18.pdf mt19.pdf mt20.pdf mt21.pdf mt22.pdf cat output mergedfile.pdf merge all files into one file mergedfile.pdf
pdftk input.pdf dump_data > metadata.txt dumps the current metadata to a file (edit this file in order to modify/add a new toc, see youtube)
pdftk input.pdf update_info_utf8 metadata.txt output input_with_toc.pdf add a toc to input.pdf, where metadata.txt contains the toc, see youtube

other

command description
pyTranscriber generates subtitles for .mp3 files via Google Speech Recognition API using Autosub (GUI)
command description
goldendict dict for fast lookup (ctrl + c + c)
command description
pycharm-community  
command description
docker  
command description
eog picture viewer (shortcuts)
command description
pinta picture editor (shortcuts)
command description
gedit texteditor
zum Lesen: unter F10/Preferences/Font & Colors/ Font ändern zu “TeX Gyre Termes Math Regular”
ctrl + h find and replace (halte im “Find & Replace”-Fenster alt gedrückt für schnelle Auswahl der Optionen)
F10 menu (u.a. Shortcuts)
F1 help, Shortcut overview
command description
kazam screen recorder
command description
joplin Notes
alt + entsprechende Taste im menu im Menu stehen alle Shortcuts !
ctrl + l change view (editor/markdown viewer/both)
F10 show all notebooks sidebar
F11 show all Notes sidebar
ctrl + shift + l focus note selection
ctrl + shift + b focus body
ctrl + shift + n focus title
command description
dconf-editor zB gsettings set org.gnome.desktop.interface clock-show-weekday true geht irgendwie nicht, stattdessen in dconf-editor zu org.gnome.desktop.interface navigieren und clock-show-weekday aktivieren.
command description
lm-sensors get CPU temperature (using command sensors)
command description
telegram-desktop Telegram
zoom-client  
discord  
command description
ticker stock monitor
command description
Tor-Browser-Bundle Webdownload installation: see here
command description
inxi -Fxz inxi - Command line system information script for console and IRC
inxi -G get Graphics info, eg. display resolution, GPU, etc.
command description
cuda installation via .deb file
nvidia-cuda-toolkit manuell installiert mit sudo apt install nvidia-cuda-toolkit, nachdem cuda per .deb file installiert wurde
nvidia-docker2 installation
command description
droidcam use Android smartphone cam as Ubuntu webcam
command description
psensor CPU and GPU temperature, Unter “sensor preferences” im Tab “Application Indicator” das Kästchen “Display sensor in the label” aktivieren, damit ein bestimmter Wert im System Tray angezeigt wird.
conky see configuration
command description
mailspring mail client similar to Apple Mail
command description
peek screen2gif recorder
command description
sqlite3 A command line interface for SQLite version 3
sqlitebrowser light GUI editor for SQLite databases
command description
sudo apt-get install gnome-tweaks GNOME tweak tool
command description
sudo apt-get install dconf-editor dconf editor
command description
plank dock similar to macOS
command description
whatsapp-for-linux whatsapp
command description
1. sudo apt-get install compiz compiz-gnome compiz-plugins-extra compiz Fenstermanager dependencies
2. sudo apt install compizconfig-settings-manager compiz Fenstermanager
command description
doxygen create class diagram for C++ projects (Doxygen is a documentation system for C++, C, Java, Objective-C, IDL (Corba and Microsoft flavors), Fortran, Python, VHDL and to some extent PHP, C#, and D.)
doxywizard a tool to configure and run doxygen on your source files
command description
qt5 installiere via offline installer qt-opensource-linux-x64-5.9.5.run, weil qtcreator nur so automatisch qt konfiguriert (s. bookmarks in CS\/coding\/docker\/)
qtcreator for GUI development
command description
python2.7 einfach per apt install python2.7 installieren (Achtung: some apps also need python2.7-dev!); starten per python2.7 (nur python2 geht nicht!)
command description
ocrmypdf ocrmypdf in.pdf out.pdf
command description
ipad_charge github link automatically start charging ipad when connected to ubuntu
command description
(nicht mehr) sudo apt install powerline maybe install https://github.com/powerline/fonts, if symbols (e.g. branch symbol in git repo) are not displayed correctly
sudo apt install fish install fish shell (add exec fish in .bashrc to start automatically; in fish_config theme fish default wählen)
curl https://raw.githubusercontent.com/oh-my-fish/oh-my-fish/master/bin/install | fish install oh my fish (necessary for bobthefish)
omf install bobthefish install powerline in fish
command description
sudo snap install postman http client
command description
dive for docker image dependencies tree (see github repo)
command description
barrier share keyboard and mouse between multiple computers (client-server model) [Note: uncheck “enable SSL” box in barrier “Menu” -> “Change Settings” (on all devices)]
command description
backgroundremover pip install backgroundremover and then download u2net.pth from https://drive.google.com/uc?id=1ao1ovG1Qtx4b7EoskHXmi2E9rp5CHLcZ (or https://drive.google.com/file/d/1ao1ovG1Qtx4b7EoskHXmi2E9rp5CHLcZ/view) and save it as /home/bra-ket/.u2net/u2net.pth
command description
v4l2-ctl for setting webcam powerline frequency (see below)
command description
sudo apt install fzf general-purpose command-line fuzzy finder
apt-cache show fzf will show Refer /usr/share/doc/fzf/README.Debian for quick instructions on how to add keybindings for Bash, Zsh, Fish to call fzf.
vim /usr/share/doc/fzf/README.Debian how to source fzf
command description
sudo apt install fd-find fast alternative to find
ln -s $(which fdfind) ~/.local/bin/fd because the binary name fd is already used by another package
command description
sudo apt install keepass2 password manager
command description
sudo apt install gpick color picker (get hex code of a color by pointing with the mouse at some point on the screen, stackoverflow)

Dotfiles

Versioning: see atlassian.com

My aliases

alias listssids='/System/Library/PrivateFrameworks/Apple80211.framework/Versions/Current/Resources/airport /usr/local/bin/airport'

In ~/.bashrc (Ubuntu default): alias l='ls -CF'
alias la='ls -A'
alias ll='ls -alF'
(die restlichen Ubuntu alias gehen nicht bei Macbook Pro Mid 2010 wegen Doppelbindestrich Argument --color=auto)

In ~/.bash_aliases:

alias phth_ticker='ticker --config ~/snap/ticker/common/.ticker.yaml'

command description
alias List all aliases
type some_alias check the meaning of a specific alias

System Folder

command description
~/.local/share/Trash/files rm FILE command moves FILE to this location

General commands

command description
ctrl + r + Suchbegriff reverse search (mehrmals ctrl + r drücken, um zwischen den Suchbegriff enthaltenden commands auszuwählen, danach -> um zu übernehmen bzw Enter um auszuführen)

Root

command description
sudo an acronym for SuperUser & Do or Switch User & DO
sudo -i run single command with root privileges (does not require root password !)
sudo -s run single command with root privileges (does not require root password !) + do not change user and working directory
su switches to super user (root user) (requires root password !) (in Ubuntu: root account disabled by default for improved security)
su - - (-l, --login) flag: the shell switches from its original directory to a login shell that simulates an actual login.
sudo su postgres Switches to the specified user’s account (here: postgres) and it will inherit the original user’s environment variables to target user
sudo su - postgres Switches to the specified user’s account (here: postgres), but does not inherit the original user’s environment variables, instead it resets all environment variables and creates them again

Job Control

jobs

command description
jobs list all jobs of the current shell
jobs -l show the PID of each job
jobs -p shows just the PIDs

bg

  • some_command &: run process some_command in the background
    • bg: alternatively, once you’ve started a process, you can background it by first stopping it (hit ctrlz) and then typing bg to let it resume in the background. It’s now a “job”, and its stdout/stderr/stdin are still connected to your terminal., superuser
    • terminal exit, ctrld: sends SIGHUP to all jobs in the closed shell’s job list
    • note: & is a control operator and you are only allowed to put one of those at the end of a simple command, thus, in bash one-liners you must write some_command & next_command and not some_command &; next_command

nohup, disown

good explanation: superuser

  • nohup gedit &: start gedit in the background AND do not stop gedit (do not send SIGHUP to gedit), when shell is stopped. (Dies war ein einfaches Beispiel, aber es macht den eigentlichen Nutzen klar, wenn man z.B. per SSH auf einem fremden Rechner arbeitet und dort einen langwierigen Prozess starten möchte, die ssh-Verbindung aber während des Prozesses nicht permanent aktiv sein soll, weil man etwa den eigenen Rechner ausschalten möchte.)
  • disown <tab>, eg. psensor & followed by disown "%psensor": a bash builtin that removes a shell job from the shell’s job list. What this basically means is that you can’t use fg, bg on it anymore, but more importantly, when you close your shell it won’t hang or send a SIGHUP to that child anymore. Unlike nohup, disown is used after the process has been launched and backgrounded., superuser

Main disadvantages:

  • dangerous: rm -r symlinkToDirectory/ deletes the contents of the symlinked directory, stackoverflow
    • whereas rm -r symlinkToDirectory deletes the symlink only

Main advantages:

  • when you need to have a folder in multiple locations on your machine
    • Saves storage by avoiding duplicate folders on the machine
    • Better versioning by avoiding duplicate folders on the machine
command description
ln -s path/to/existing/FILE path/to/LINK create a symlink to a file (no / at the end of the paths!)
ln -s path/to/existing/DIR path/to/LINK create a symlink to a directory (no / at the end of the paths!)
readlink -f LINK show symlink target [ACHTUNG: das heißt nicht, dass das target auch existiert, s.i LINK !]

Open Files from the Terminal

command description
xdg-open file open file using default application
gio open file same as xdg-open, but depends on what desktop the user has installed, whereas xdg-open is desktop agnostic

Process Management

command description
top activity monitor
ps wie top, aber keine real-time updates (dh. nur ein snapshot)
ps -eo pid,lstart,cmd \| grep 2127686 start time of PID 2127686 (e.g. to get terminal start time, run echo $$, and then this command)
echo $$ show PID of current shell
kill PID stop process with id PID, sends SIGTERM (i.e. kills gracefully) (see notes bash and kill doc)
pkill process_name stop all processes containing process_name (which is a regular expression), sends SIGTERM (i.e. kills gracefully), Warning: use pgrep first to check which processes will be killed
pgrep process_name list all PIDs containing process_name (which is a regular expression)

Check PID of a window (pick a window with the cursor):

xprop _NET_WM_PID | sed 's/_NET_WM_PID(CARDINAL) = //' | ps `cat`

This will make your cursor a cross with which you can click on an open window. It will report the PID and command in the terminal you ran it in.

In general, xprop and xwininfo will provide you with a lot of information about an open window.

Get Paths

command description
realpath foo.bar get path to file “foo.bar” (like pwd + foo.bar)
readlink -f foo.bar get path to file “foo.bar” (like pwd + foo.bar)

Redirection, Pipe Tricks

command description
ls \| wc -l count files in a directory
history \| tail -n 30 show last 30 commands

comm

To compare just the filenames in dir1 and dir2:

linuxquestions.org

comm <(ls dir1) <(ls dir2)

The output will be differentiated by 0, 1, or 2 leading tabs as:

files only in dir1 files only in dir2 files in both dirs

Options to comm allow selection of the columns you want.

diff

groups.google.com

Compare listings of two directories using process substitution in bash:

diff <(ls dir1) <(ls dir2)

Differences between two directory trees

command description
diff -r dir1/ dir2/ outputs exactly what the differences are between corresponding files
diff -qr dir1/ dir2/ just getting a list of corresponding files whose content differs
diff -qrN dir1/ dir2/ to see differences for files that may not exist in either directory

apt, apt-get, snap, dpkg, pkg-config

Difference between apt and apt-get + apt-cache:

  • apt = most commonly used command options from apt-get and apt-cache see here
  • So with apt, you get all the necessary tools in one place. You won’t be lost under tons of command options. The main aim of apt is to provide an efficient way of handling packages in a way “pleasant for end users”.
  • apt:
    • shows progress bar while installing or removing a program
    • prompts number of packages that can be upgraded when you update the repository database (i.e. apt update)
    • same can be achieved with apt-get (but you need additional options)
  • When you use apt to install a package, under the hood it uses dpkg. When you install a package using apt, it first creates a list of all the dependencies and downloads it from the repository.
    • Once the download is finished it calls dpkg to install all those files, satisfying all the dependencies.
command description
sudo apt update  
sudo apt [-y] upgrade -y oder —yes für automatic yes to prompts
apt --help  
sudo apt remove package uninstall package_file.deb
sudo apt autoremove remove not needed packages (NOTE: This command will remove all unused packages (orphaned dependencies). Explicitly installed packages will remain.)
sudo apt-mark auto $PACKAGES mark packages in variable PACKAGES as automatically installed, if accidentally marked as manually installed

apt

Include directories for C++

  • /usr/local/include/
    • e.g. /usr/local/include/opencv4/opencv2/
  • /opt/
    • e.g. /opt/ros/

PPAs

Personal Package Archives (PPAs) are software repositories designed for Ubuntu users and are easier to install than other third-party repositories. PPAs are often used to distribute pre-release software so that it can be tested. (source)

Adding PPAs:

# add repository
sudo add-apt-repository ppa:whatever/ppa

Removing PPAs:

# remove repository
sudo add-apt-repository --remove ppa:whatever/ppa

You can also remove PPAs by deleting the .list files from /etc/apt/sources.list.d directory.

Install

command description
sudo apt install ./name.deb install a .deb file
sudo apt-get install <package name>=<version> install a specific version

Uninstall

command description
sudo apt purge ... Removing packages with sudo apt purge ... or sudo apt --purge remove ... will remove them and all their global (i.e., systemwide) configuration files. This is usually what people mean when they talk about completely removing a package. This does not remove packages that were installed as dependencies, when you installed the package you’re now removing. Assuming those packages aren’t dependencies of any other packages, and that you haven’t marked them as manually installed, you can remove the dependencies with sudo apt autoremove or (if you want to delete their systemwide configuration files too) sudo apt --purge autoremove.
sudo apt --purge remove ... see sudo apt purge ...
sudo apt autoremove remove the dependencies that are no longer needed
sudo apt --purge autoremove remove systemwide configuration files and the dependencies that are no longer needed

apt-cache

command description
apt-cache policy <package name> shows installed package version and also all the available versions in the repository according to the version of Ubuntu in which you are running
apt-cache search <package_name> find specific package names

apt-mark

command description
sudo apt-mark hold package_name hold packages (i.e. do not upgrade, remove or modify package_name)
sudo apt-mark unhold package_name unhold “held” packages
apt-mark showhold show held packages

dpkg

command description
sudo dpkg -l \| less list all installed dpkg packages meaning of tags ii, rc, …
sudo dpkg -L package show all files which were installed by a package
sudo vim /var/lib/dpkg/info/nvidia-cuda-toolkit.list in /var/lib/dpkg/info/ sind die installation files (.conffiles, .list, .md5sums) für alle packages (hier: nvidia-cuda-toolkit)
dpkg -l \| grep ^..r list all broken packages (r state (on the third field) means: reinst-required (package broken, reinstallation required))

Basics

command description
sudo dpkg -i package_file.deb install package_file.deb (alternative: sudo apt install ./name.deb)
sudo dpkg -P some_package purge some_package
sudo dpkg -r some_package remove some_package

Confirm Whether Package Is Already Installed

Tipp: AM BESTEN DIE FOLGENDEN 3 ALLE AUSFÜHREN, DA JEDER EINEN ANDEREN OUTPUT HAT !

ACHTUNG: bei allen folgenden commands den exakten Namen schreiben, zB lua findet lua5.1 nicht !

command description
sudo dpkg -l package confirm whether package is already installed (wenn nicht installed, dann wird no packages found matching package angezeigt)
sudo dpkg -l \| grep package confirm whether package is already installed (wenn nicht installed, dann wird nichts angezeigt)
sudo dpkg-query -s package prüfe ob package installiert ist und print weitere Informationen zum package

Show History Of Installed Packages

see also how-to-show-history-of-installed-packages

command description
grep " install \| remove " /var/log/dpkg.log list recently installed OR removed packages (in the current month)
grep " install " /var/log/dpkg.log.1 list recently installed packages (in the previous month)
zgrep " install " /var/log/dpkg.log.2.gz list recently installed packages (go back 2 months, same for >2 months)
vim /var/log/apt/history.log view apt history

snap

  • see man snap for details
  • updates: according to Snap tutorial Snaps are automatically updated in the background once per day., askubuntu
    • However, if you don’t close the application it will not be updated and you will receive daily notifications to do so. askubuntu
command description
snap list  
snap find package  
sudo snap install package  
sudo snap remove package  
sudo snap remove –purge package  

pkg-config

command description
man pkg-config description of all pkg-config flags
pkg-config --libs-only-l json-c was man im CMakeLists.txt in target_link_libraries eintragen muss (hier: -ljson-c Achtung: das -l muss auch im CMakeLists.txt rein!)
pkg-config --libs-only-L json-c location of .so library file (hier: in ubuntu 18.04: findet er nicht, ist aber in /lib/x86_64-linux-gnu; in ubuntu 20.04: -L/usr/local/lib) (see also: difference .so vs .a libraries) (muss nicht in CMakeLists.txt rein, s. Minimalbsp)
pkg-config --cflags json-c include paths of the corresponding library with .h header files (hier: in ubuntu 18.04: -I/usr/include/json-c; in ubuntu 20.04: -I/usr/local/include -I/usr/local/include/json-c) (muss nicht in CMakeLists.txt rein)

tty, terminal session management

From stackexchange:

  • A tty (teletype) is a native terminal device, the backend is either hardware or kernel emulated.
  • A pty (pseudo-tty) is a terminal device which is emulated by another program (example: xterm, screen, or ssh are such programs).
  • A pts is the slave part of a pty.
  • More info: see stackexchange and man pty
command description
tty zeigt Namen des aktiven terminals
ls -ltr /dev/ttys* zeigt Namen aller aktiven terminals
last zeige letzte terminal logins
whoami print the user name associated with the current effective user ID

chmod, Groups

Default Permissions:

From baeldung:

  • On Linux, by default, when we create new files, they are given rw-rw-r– permissions.
    • The first rw- signifies read-write permissions for the user or the owner of the file
    • The second rw- indicates read-write permissions for the group the file belongs to
    • The final r– read permission is for all other users
  • Similarly, for newly created directories, the default permission is rwxrwxr-x.
command description
chmod permissions-file is an abbreviation of change mode. A file’s mode is the set of permissions attached to it that control access. Zu permissions: s. here.
command description
groups list all groups the currently logged in user belongs to (first group is the primary group)
groups user same as groups, but for specific user user
id ”
id user ”
command description
less /etc/group view all groups present on the system
cat /etc/group ”
getent group ”
command description
getent group docker list all members of group docker
command description
sudo groupadd docker add new group docker
sudo usermod -aG docker $USER add my user to the docker group
newgrp docker log out and log back in so that group membership is re-evaluated (nach group Aenderungen); wenn das nicht geht, reboot

useradd, usermod, deluser

source: baeldung

Run these commands as root user. Run them in TTY mode (press e.g. ctrl + alt + F3).

command description
sudo passwd root set the root’s password
ctrl + alt + f1 or ctrl + alt + f2 … switch the TTY in order to log in as root
sudo useradd -m baeldung creating a user called baeldung, in the default way
sudo useradd -m -d /home/baeldung baeldung (important: do not use a slash character at the end of /home/baeldung, otherwise the terminal will show /home/baeldung instead of the ~ symbol at the start of each line !) create a user and set the location for the home directory at the same time
sudo usermod -d /usr/baeldung baeldung change the user’s home directory to /usr/baeldung
sudo usermod -m -d /usr/baeldung baeldung also move the existing content to the new location
startx start the Ubuntu GUI when you are in the tty
sudo deluser --remove-home userName delete user userName

bash

Change Terminal Title

Change the title of the current terminal: echo -ne "\033]0;SOME TITLE HERE\007", askubuntu

Gnome Terminal Shortcuts

jumping with command line cursor

command description
ctrl + w delete the word in front of the cursor
esc + backspace delete a part of a path in front of the cursor (e.g. to get from this/is/some/path to this/is/some/)
alt + d delete the word after the cursor
ctrl + a jump to the beginning of the line
ctrl + e jump to the end of the line
ctrl + s freeze/block terminal
ctrl + q unfreeze/unblock terminal
fn + links scrolle nach ganz oben
cmd + oben focus letzte input Zeile (zB gut, wenn man zB schnell hochscrollen will)

Bash Scripting

Change Shell

command description
echo $$ display PID of current shell
echo $0 check current shell type
bash start new bash shell instance in current bash shell (the new shell will have a different PID than the old one, check shell PID via echo $$)
cat /etc/shells list all shells
chsh change shell (you will be prompted to enter one of the shells in cat /etc/shells)

env, PATH

command description
printenv Print the values of the specified environment VARIABLE(s).
env show all environment variables
env NAME=VALUE Set each NAME to VALUE in the environment
echo $PATH spezielle Variable, die alle Pfade enthält, in denen Shell-Programme/Shell-Befehle (ls, echo, df, nautilus, etc.) gesucht werden
echo $Variable display the content of the variable “Variable”

Running Multiple Commands

command description
do_something1 && do_something2_that_depended_on_something1 only run “something2”, if “something1” completes successfully
do_something1; do_something2 run “something2” irrespective of “something1”

ls

command description
ls -d */ list directories only
ls -d /etc/*/ list directories only in a specific directory

find

  • Best Practices:
    • put the search pattern in quotes, otherwise you might get the error paths must precede expression
command description
find /opt/ -iname "pattern" find all files (hier: in dir /opt/ ), for which base of file name (path with leading dirs removed) matches shell pattern pattern (Achtung: pattern muss genau übereinstimmen! Falls Endung unbekannt, mit Sternchen * am Ende suchen, dh. pattern* statt pattern suchen (wie bei ls Befehl).
find /opt/ -name "pattern" wie -iname, aber case-sensitive
find /opt/ -iname "pattern" -type f nur files suchen
find /opt/ -iname "pattern" -type d nur dirs suchen
find /opt/ -iname "pattern1" -iname "pattern2" logical “AND”
find /opt/ ! -iname "pattern1" logical “NOT”
find /opt/ ( -iname "pattern1" -o -iname "pattern2" ) logical “OR”
find /opt/ ( -iname "pattern1" -or -iname "pattern2" ) logical “OR”, not POSIX compliant
find /opt/ -size +1G nur files, die über 1GB groß sind
find . -iname "pattern" -printf '%Tc %p\n' show timestamps (modified time)
find . -newermt "2024-07-26" -not -newermt "2024-07-27" find by modified time
find /path/to/dir -newermt "yyyy-mm-dd HH:mm:ss" -not -newermt "yyyy-mm-dd HH:mm:ss+1" list file in the folder /path/to/dir modified between yyyy-mm-dd HH:mm:ss and yyyy-mm-dd HH:mm:ss + 1 second, unix.stackexchange
find /path/to/dir -newerat find by access time
find /path/to/dir -newerct find by creation time
find . -regextype sed -regex ".*/[a-f0-9\-]\{36\}\.jpg" regex, there’s an implicit ^ ... $ surrounding your regex (it must match the WHOLE result line), valid types are 'findutils-default', 'awk', ' egrep', 'ed', 'emacs', 'gnu-awk', 'grep', 'posix-awk', 'posix-basic', 'posix-egrep', 'posix -extended', 'posix-minimal-basic', 'sed'
find . -iname "searchPattern" -print0 \| xargs -0 someCommand apply someCommand on each of the found files
find . -iname "searchPattern" -print0 \| xargs -0 du -sh show the size of each found file
find . -iname "searchPattern" -exec rm -v "{}" \+ remove the found files; from man find: -exec: “The specified command is run once for each matched file.”; +: best explanation: stackoverflow
find path_A -name '*AAA*' -exec mv -t path_B "{}" \+ move the found files

locate

command description
locate <file> faster than find, but uses a database which must be updated via sudo updatedb to find recent changes
locate -i <file> case insensitive
locate -b '\file.xyz' exact match (Note: the slash and the quotation marks are necessary)
sudo updatedb update the locate command’s database

Finding Program Paths

command description
which <program> show the path of a program
which python3  
whereis python3  

regex

  • in vim’s “find and replace”: you must escape {, }, /, (, ), |, + (but not: [, ]) and some other characters with a backslash “\” for the regex find pattern and the replace pattern to work
  • match URLs: https?:\/\/(www\.)?[-a-zA-Z0-9@:%._\+~#=]{1,256}\.[a-zA-Z0-9()]{1,6}\b([-a-zA-Z0-9()@:%_\+.~#?&//=]*), stackoverflow
    • without http protocol: [-a-zA-Z0-9@:%._\+~#=]{1,256}\.[a-zA-Z0-9()]{1,6}\b([-a-zA-Z0-9()@:%_\+.~#?&//=]*)

Special Characters:

Char Description Meaning
\ Backslash Used to escape a special character
^ Caret Beginning of a string
$ Dollar sign End of a string
. Period or dot Matches any single character
\| Vertical bar or pipe symbol Matches previous OR next character/group
? Question mark Match zero or one of the previous
* Asterisk or star Match zero, one or more of the previous
+ Plus sign Match one or more of the previous
( ) Opening and closing parenthesis Group characters
[ ] Opening and closing square bracket Matches a range of characters
{ } Opening and closing curly brace Matches a specified number of occurrences of the previous

Quantifiers:

  • X, exactly n times: X{n}
  • X, at least n times: X{n,}
  • X, at least n but not more than m times: X{n,m}
  • related:

Character Classes:

  • \w (word)
  • \d (digit)
  • \s (whitespace)
  • \S (not whitespace)
  • (\w|\d) (word or digit)
  • (\w{1,}|\d) (at least one word or more words or exactly one digit)
  • etc

Numeric References and Capture Groups:

  • ([A-Z])\w+\1 (numeric reference \1 refers to the results of capture group number 1, which is ([A-Z]) in this example)
    • eg. in the string RegRxr was created by gskinner.com. this would match RegRxr
    • eg. in the string RegExr was created by gskinner.com. this would not match RegExr
  • this is very useful for “find and replace” in vim because you can replace text with a numeric reference, eg. :%s/\([A-Z]\)\w\+/\1/g replaces all matches of the pattern ([A-Z])\w+ with the first capture group in the find pattern (here: ([A-Z]))

Negative Lookahead:

  • word\(atom\)\@! (useful to search word not followed by atom)
    • eg. in the string RegRxr was created by gskinner.com. the vim regex R\(x\)\@! would match the R in front of Re, but not the R in front of Rx
    • eg. in the string RegRxr was created by gskinner.com. the vim regex c\(r\)\@! would match the c in front of co, but not the c in front of cr

Only match the first occurrence of a character in the line:

  • problem: ".*" will match a double quoted string only if there is only one double quoted string in the line. When there are multiple double quoted strings in the line this pattern will match from the first double quote sign " in the line until the last which is likely not intended
    • solution: use negation: "[^"]+" to match anything but " until the next "
    • example:
      • vim regex: %s/\*\*\([^\*]\+\)\*\*/<span style=>**\1**<\/span>/g

Types of regex

mostly from stackoverflow

  • POSIX Basic Regular Expressions (BRE): This is a standard syntax used in UNIX-based systems for basic pattern matching. It uses a limited set of metacharacters, including ^, $, ., *, +, ?, [, ], (, ), and .
  • POSIX Extended Regular Expressions (ERE): This is a more powerful syntax used in UNIX-based systems for more advanced pattern matching. It adds more metacharacters, including {, }, |, and ^.
    • The main difference is that some backslashes are removed: \{…\} becomes {…} and \(…\) becomes (…), wikibooks
  • Perl-Compatible Regular Expressions (PCRE): This is a syntax used in many programming languages, including Perl, PHP, and Python. It adds many advanced features, such as lookaheads, lookbehinds, named capture groups, and more.
  • JavaScript Regular Expressions: This is the syntax used by the JavaScript programming language. It is similar to PCRE but has some differences, such as the use of \b for word boundaries instead of \y.
  • .NET Regular Expressions: This is the syntax used by the .NET Framework. It is similar to PCRE but has some differences, such as the use of (?) for named capture groups instead of (?P).
  • Vim Regex

grep

  • Best Practices:
    • always exclude the ... | grep pattern command itself
      • if you cannot exclude it, then
        • in ... | grep pattern | tail -n number the tail command should come last
  • man grep:
    • “Typically PATTERNS should be quoted when grep is used in a shell”
  • single quotes vs. double quotes
  • by default, grep used BRE (use -E to use ERE)

Basics

command description
grep -c count matches, best practice: instead of grep \| wc -l
grep -i pattern case insensitive
grep -o pattern "$file" option -o to only print the matching part
l \| grep -e pattern1 -e pattern2 logical “OR”: greps pattern1 or pattern2
grep -r -E 'orange \| mango' . logical “OR” operator
l \| grep -e pattern1 \| grep -e pattern2 logical “AND”: greps pattern1 and pattern2
l \| grep -v pattern logical “NOT”: greps everything except pattern
grep -rn -e 'nvidia' /var/log/apt/history.log* r: recursively look at all files in the folder, n: show line numbers, e: regex pattern, here: nvidia (w/o this some regex patterns will not work)
grep -rnw -e 'nvidia' /var/log/apt/history.log* w: match whole words only (i.e. if the pattern nvidia is a substring of a word, it is not matched)
l \| grep 150 \| xargs rm -v pipe output of grep to rm
l \| grep xyzpattern \| xargs cp -iv -t 150/ pipe output of grep to cp
l \| grep xyzpattern \| xargs mv -iv -t 1024p/ pipe output of grep to mv
grep -n someSearchPattern n: show line numbers (useful to find things in man and long --help outputs, eg. use man command and jump to the line that command --help \| grep -n someSearchPattern shows)
grep -oE 'pattern.{0,4}' "$file" option -o to only print the matching part in combination with -E (extended regular expression) and pattern .{0,4} to match up to four characters after your search pattern, stackexchange
grep -x '.\{3,10\}' -x (also --line-regexp with GNU grep) match pattern to whole line

Spaces

How to include a space character with grep?

Make sure you quote your expression.

grep ' \.pdf' example

Or if there might be multiple spaces (we can’t use * as this will match the cases where there are no preceding spaces)

grep ' \+\.pdf' example

+ means “one or more of the preceding character”. In BRE you need to escape it with \ to get this special function, but you can use ERE instead to avoid this

grep -E ' +\.pdf' example

You can also use \s in grep to mean a space

grep '\s\+\.pdf' example

We should escape literal . because in regex . means any character, unless it’s in a character class.

nl

command description
command \| nl -w2 -s'> ' add line numbers in front of each line of the output of command, stackexchange

tee

command description
command \| tee file.txt read from standard input and write to both standard output and the file file.txt (overwrites file.txt!) doc (name derived from “T-junction”, since tee is usually used in pipes)
command \| tee -a file.txt append to file.txt
du -h \| tee disk_usage1.txt disk_usage2.txt disk_usage3.txt write to multiple files at once
ls file\* \| tee third_file.txt \| wc -l forward the output as input
echo "newline" \| sudo tee -a /etc/file.conf using tee in conjunction with sudo

awk

Get Rows

command description
<some_command> \| awk 'NR % 5 == 0' prints every fifth line

Get Columns

command description
<some_command> \| awk '{print $2}' get the 2nd column of the command output
<some_command> \| awk '{print $2, $4}' get the 2nd and 4th column of the command output
<some_command> \| awk '{print $2, $4}' get the 2nd and 4th column of the command output
<some_command> \| awk -F '"' '{print $2}' Use -F [field separator] to split the lines on "s

cut

command description
<some_command> \| cut -f2- -d' ' get all columns (delimited by a space) from the 2nd to the last column of the command output
<some_command> \| cut -f2- -d' ' tab delimiter: Press Ctrl+V and then Tab to use “verbatim” quoted insert.
history \| cut -c 8- show the history without line numbers, -c 8- deletes the first 7 characters

sed

  • for line-based input
    • thus, hard to replace \n with sed, tr is better here (stackoverflow)
  • “Sed uses basic regular expressions (BRE). In a BRE, in order to have them treated literally, the characters $.*[\^ need to be quoted by preceding them by a backslash, except inside character sets ([…]). Letters, digits and (){}+?| must not be quoted (you can get away with quoting some of these in some implementations).” (more)
  • Command Summary for sed
  • Bash Variables in sed
  • sed one liners
command description
sed 's/unix/linux/' geekfile.txt replaces the word ‘unix’ with ‘linux’ in the file ‘geekfile.txt’. sed is mostly used to replace text in a file. Examples: see here.
sed -E use extended (ERE) regular expression syntax
sed -e 's/ /\\ /g' Useful when paths contain spaces and you need to escape these spaces with backslash, eg. when using realpath, pwd, scp, etc. s/: Substitute replacement for pattern on each addressed line doc: see “s” command.
sed '0,/Apple/{s/Apple/Banana/}' input_filename replace only the first occurrence in a file, “The first two parameters 0 and /Apple/ are the range specifier. The s/Apple/Banana/ is what is executed within that range. So in this case “within the range of the beginning (0) up to the first instance of Apple, replace Apple with Banana. Only the first Apple will be replaced.”, stackoverflow
sed 's/$/ pattern/' filename appending pattern to end of a line
sed '/Fred Flintstone/ s/$/ pattern/' filename append only to lines containing a specific string
sed '/pattern/{G;}' filename add a newline after a pattern

tr

  • to replace single characters by single characters, stackoverflow
  • tr SET notation
  • hard to replace \n with sed, tr is better for this task (stackoverflow)
    • pipe with tr a b | sed -e 's/find/replace/g' to replace strings
command description
tr '\n' ' ' replace all \n with spaces, tr SET notation
tr -d '\n' delete all \n, tr SET notation

head, tail

command description
command \| head -3 show the first 3 rows of the output of command
command \| tail -3 show the last 3 rows of the output of command
command \| tail +3 show all rows starting at row 3 of the output of command
command \| tail +24 \| head -100 show the first 100 rows starting at row 24 of the output of command
tail -n +10 input.txt \| head -n 91 prints rows 10-100, ie. tail -n +10 prints out the entire file starting from line 10, and head -n 91 prints the first 91 lines of that (up to and including line 100 of the original file)

redirection

command description
exec > some_file redirect all shell output to some_file
ls -ltr \| vim - zeige Output eines Befehls in vim (ACHTUNG: Leerzeichen hinter “vim” nicht vergessen!)
echo "blabla" >> filename write output to file filename
echo "blabla" \| tee filename write output to file filename

Open in File Browser

command description
nautilus . öffne current directory in File Browser

comments

command description
# ein comment Kommentar in command line

time, date

command description
date use date --help for formatting options
date '+%m-%d-%y' for 06-30-24 format

dirs, pushd, popd

command description
dirs print the directory stack (left to right)
dirs -v print the directory stack (one entry per line), prefixing each entry with its index in the stack, doc
pushd path/to/somedir Adds a directory to the top of the directory stack, doc
pushd +N Brings the Nth directory (counting from the left of the list printed by dirs, starting with zero) to the top of the list by rotating the stack, doc
popd +N Removes the Nth directory (counting from the left of the list printed by dirs), starting with zero, from the stack, doc
popd -N like popd +N, but counting from the right

cd, mkdir, pwd

command description
pwd zeige current working directory
cd path/to/somedir  
cd go to home directory
mkdir -p /folder/subfolder/subsubfolder erstellt folder und subfolder automatisch, falls sie noch nicht existieren

mv, rm, cp, rename

command description
mv -iv Tipp: IMMER -iv BENUTZEN! (-i für bestätigen, -v für ausgeführte Aktion zeigen)
mv "$file" "${file%???????}" # 7 question marks to match 7 characters rename file and remove the last 7 characters of the filename
rename 's/pattern/replacepattern/' *.jpg rename all .jpg files by replacing pattern with replacepattern in their filenames (sudo apt install rename)
rm -iv Tipp: IMMER -iv BENUTZEN! (-i für bestätigen, -v für ausgeführte Aktion zeigen)
cp -iv Tipp: IMMER -iv BENUTZEN! (-i für bestätigen, -v für ausgeführte Aktion zeigen)
find ../path/to/search/ -iname *searchpattern* -exec cp -iv "{}" ./destination/folder/ \; find and copy the found files
cp -a attempts to make a copy that’s as close to the original as possible: same directory tree, same file types, same contents, same metadata (times, permissions, extended attributes, etc.). Always use cp -a instead of cp -r. (see cp -a vs cp -r)

history, script

command description
history get a list of the last 1000 commands
history \| grep command_to_search search some pattern within the history generated list
script start saving all input and output in the current terminal session in the file typescript (end recording via ctrl + d - this does not close the terminal here; use script /path/to/mylogfile.txt to save it in /path/to/mylogfile.txt; typescript will be overwritten if you start script twice without providing a name!). source

xclip, xsel

  • xclip and xsel are very similar!
  • xclip and xsel can store text into 3 different selections (by default it is primary selection)
  • the two main selections are:
    • Primary selection is basically what you high-light and released with the middle mouse click (which corresponds to pressing both right and left touchpad key on a laptop).
    • The clipboard is the traditional Ctrl V.
command description
xsel -bc clear clipboard
command \| xclip copy the output of command and place it in XA_PRIMARY (the “primary selection”)
command \| xclip -sel prim same as command \| xclip
command \| xclip -sel clip copy the output of command and place it in XA_CLIPBOARD (“the clipboard”)
xclip -o print a selection to standard out
xclip -o \| xclip -sel clip Copy XA_PRIMARY to XA_CLIPBOARD
pwd \| tr -d '\n' \| sed 's/$/\//g' \| xclip -selection c copy the output of pwd into the clipboard (without the linebreak at the end)

wmctrl

sudo apt install wmctrl

From superuser.

List Windows

  • wmctrl -l (list windows)

Focus Windows

  • wmctrl -a window-name (go to workspace and focus by window name)
    • map this to alt + shift + 1,2,3,etc. (after renaming the windows properly, renaming command: see below)
  • wmctrl -i -a 0x066f5d24 (go to workspace and focus by window ID)

Rename Windows

  • wmctrl -i -a 0x066f5d24 -T "new-name" (rename window)

With xdotool

Unzipping

command description
unzip file -d destination unzip to destination
tar -C ./data/ -zxvf ~/Downloads/mnist.tgz für .tgz (wobei -C target_location -zxvf source.tgz), .tar.gz
oder andersrum:  
tar -zxvf ~/Downloads/mnist.tgz -C ./data/  
tar -C ./data/ -jxvf ~/Downloads/datei.tar.bz2 für .tar.bz2 (dh. -j flag statt -z flag)
tar -C ~/ -xvf tor-browser-linux64-10.5.2_en-US.tar.xz für .tar.xz
zip -FF 210211.zip --out 210211-2.zip -fz “fix” a broken zip file, then run unzip 210211-2.zip, stackexchange

Convert

command description
find . -iname "*.txt" -exec bash -c 'mv "$0" "${0%\.txt}.md"' {} \; txt2md:

System information

Software

Note: lsb_release and uname may report different Kernel versions!

command description
cat /etc/os-release Ubuntu Version (lang)
cat /etc/lsb-release Ubuntu Version (lang)
lsb_release -a Ubuntu Version (kurz)
lsb_release -cs Ubuntu Version (e.g. “focal”)
hostnamectl Ubuntu Version (mittel) mit Linux Kernel Version
uname –help Returns the help manual for the uname command, including all available options.
uname -a Prints all information for the server/system you’re on.
uname -s Prints the kernel name
uname -n Prints the node name
uname -r Prints the kernel release data
uname -v Prints the kernel version data
uname -m Prints the machine data
uname -p Prints the processor information
uname -i Prints the platform hardware information
uname -o Prints the operating system information

Hardware

command description
lscpu  
lshw  
hwinfo –short  
lspci  
lsscsi  
lsusb  
inxi -Fx  
lsblk list block devices, e.g. to see all drives attached to your system, including their sizes and partitions
df -H  
pydf  
sudo fdisk -l  
mount \| column -t  
command description
sudo dmidecode -t processor  
sudo dmidecode -t memory  
sudo dmidecode -t bios  
command description
cat /proc/cpuinfo  
cat /proc/meminfo  
cat /proc/version  
cat /proc/scsi/scsi  
cat /proc/partitions  

Memory

command description
free -m  
watch free -m update every 2 seconds
dmesg -T \| grep oom-killer -T: show timestamps; shows the OutOfMemory-killer at work. This should not show any output! If it does, it is a bad sign!

GPU

command description
nvidia-smi -q -d temperature temperature info including critical temperature values, shutdown temperature etc.
nvidia-smi –query-gpu=name –format=csv get GPU name

Udev

Udev is the Linux subsystem that supplies your computer with device events. In plain English, that means it’s the code that detects when you have things plugged into your computer, like a network card, external hard drives (including USB thumb drives), mouses, keyboards, joysticks and gamepads, DVD-ROM drives, and so on.

  • udev scripting: see tutorial
    • how to create a udev script triggered by some udev event, such as plugging in a specific thumb drive
command description
udevadm monitor tap into udev in real time and see what it sees when you plug in different devices. The monitor function prints received events for: UDEV: the event udev sends out after rule processing, KERNEL: the kernel uevent
udevadm control --reload should load all rules (but reboot if you want to be sure)

Display

command description
xrandr list all display modes; set the size, orientation and/or reflection of the outputs for a screen; can also set the screen size
xrandr --fb 2560x1440 set the screen resolution, when no physical display is connected (e.g. when connecting to Jetson AGX via Teamviewer or VNCviewer, put this in /etc/xdg/autostart/resolution_screen_teamviewer.sh, chmod +x /etc/xdg/autostart/resolution_screen_teamviewer.sh, create /etc/xdg/autostart/resolution_screen_teamviewer.desktop and reboot and connect via Teamviewer again)

Storage

command description
diskutil list  
diskutil info /dev/disk2s2  
command description
sudo diskutil mountDisk /dev/disk2s2 (Partitionsname disk2s2 steht in rechter Spalte bei diskutil list; /dev/disk2 mounted alle Unterpartitionen)
sudo diskutil umountDisk /dev/disk2s2  
mount_ntfs -o r "/Volumes/Volume node" (r für read-only; rw für read-write (NICHT MACHEN! Es gibt einen Grund warum das bei Mac per default nicht geht!)
command description
df zeige alle Laufwerke, ganz rechts steht die Location mit dem Inhalt des Datenträgers (zB /media/bra-ket/UBUNTU 20_0)
sudo fdisk -l wie df, aber mehr Details
lsusb list usb devices
lsblk list block devices

Block Device vs. Character Device

unix.stackexchange:

“Probably you will never be able to find a simple definition of this. But in the most general and simplistic way, if you compare a character device to a block device, you can say the character device gives you direct access to the hardware, as in you put in one byte, that byte gets to the hardware (of course it is not as simple as that in this day and age). Whereas, the block device reads from and writes to the device in blocks of different sizes. You can specify the block size but since the communication is a block at a time, there is a buffering time involved.”

“Think of a block device as a hard disk where you read and write one block of data at a time and, the character device is a serial port. You send one byte of data and other side receives that byte and then the next, and so forth and so on.”

Storage, Hard Disk, HDD, SSD

Must knows:

  • SSD
    • fragmentation
    • wear leveling
    • wear leveling: As the term suggests, wear leveling provides a method for distributing program and erase cycles uniformly throughout all of the memory blocks within the SSD. This prevents continuous program and erase cycles to the same memory block, resulting in greater extended life to the overall NAND flash memory.
command description
hdparm get statistics about the hard disk, alter writing intervals, acoustic management, and DMA settings. It can also set parameters related to drive caches, sleep mode, power management, acoustic management, and DMA settings
sudo hdparm -I /dev/sda Request identification info directly from the drive, which is displayed in a new expanded format with considerably more detail than with the older -i option. (source: man hdparm -I); may differ from information provided by -i option! (source: man hdparm -i)

Eject

  1. press on eject button for all partitions in nautilus
  2. open gnome-disks
  3. press on stop button below all partitions, if any partition is still mounted (else no stop button should be available)
  4. press power off button in the top bar (only after all partitions have been unmounted in step 3!)
  5. disk LED will be turned off now
  6. close gnome-disks via alt + F4
command description
sudo eject /media/SDD  

Troubleshooting:

  1. One or more applications are keeping the volume busy
command description
sudo fuser -mv /media/SDD displays all processes accessing /media/SDD, where the m tells it to look on the given location, the v switches the output to a human readable list instead of just a bunch of PIDs. askubuntu
  1. Disconnecting from filesystem notification does not disappear automatically when ejecting an external hard drive (by pressing the eject button in Nautilus)
  • Possible Solutions that worked once:
    • close all Nautilus/Dolphin windows that access the external hard drive
    • press ctrl + c on some file that is stored on the internal hard drive (if ctrl + c was pressed on some file that is stored on the external hard drive, this will block the external hard drive when you try to eject it)
  1. in gnome-disks: External hard drive shows a “loading” symbol and the power off button for this external hard drive is grayed out
  • Possible Solutions that worked once:
    • just wait
    • close gnome-disks and open it again
    • after a while the power off button for this external hard drive is not grayed out any more and the physical LED on the hard drive stops blinking

du, Disk Usage

$ du --help
 [ ... ]
 Display values are in units of the first available SIZE from --block-size,
 and the DU_BLOCK_SIZE, BLOCK_SIZE and BLOCKSIZE environment variables.
 Otherwise, units default to 1024 bytes (or 512 if POSIXLY_CORRECT is set).
command description
ncdu like du -sh, but more convenient (because avoids typing)
du -sh *  
du -sh ./*/ show directories only
du -sch * -c to show grand total
du -sh \* \| sort -h “ascending”: largest file in the last output line
du -sh \* \| sort -rh “descending”: largest file in the first output line (-r for “reverse order”)
du -sch ./folder \| sort -rh \| head -5 zeige disk usage (=size) of folder (-h für human readable; -c für zeige grand total am Ende) (sort -rh für sortiere nach size, wobei -r für reverse und -h für compare human readable sizes)
du -sh * .[^.]* show hidden files, too (.[^.]* aka .[!.]* is a “globbing pattern”)
du -h -d 1 * -d 1 or --max-depth=1 display the sizes of only the directories immediately within the specified path. If we were to specify 2 it would go a level further.
du -h -d 1 -t 1G / -t: threshold, show the sizes of all first level directories larger than 1GB within the root / path
command description
df -h to analyze the whole filesystem

Camera

command description
mpv /dev/video0 check, if device /dev/video0 is the webcam
vlc v4l2:///dev/video0 check, if device /dev/video0 is the webcam
mplayer tv://device=/dev/video0 check, if device /dev/video0 is the webcam
gst-launch-1.0 v4l2src device=/dev/video2 name=cam_src ! videoconvert ! videoscale ! video/x-raw,format=RGB ! queue ! videoconvert ! ximagesink name=img_origin check, if device /dev/video2 is the webcam
v4l2-ctl --list-devices list cameras
v4l2-ctl -d /dev/video0 --list-ctrls show all settings
v4l2-ctl -L -d /dev/videoN list available settings of camera /dev/videoN
v4l2-ctl -d /dev/video0 --list-formats-ext show all supported camera resolutions
v4l2-ctl --set-ctrl power_line_frequency=0 -d /dev/videoN set powerline frequency (50Hz vs 60Hz) of camera /dev/videoN
v4l2-ctl -d /dev/video2 --list-formats-ext check supported pixel formats, fps and resolutions of camera /dev/video2
v4l2-ctl --device /dev/video3 --set-ctrl=zoom_absolute=120 zoom in

curl, wget

curl and wget are retrieval commands.

command description
wget -nc -nc for “do not overwrite existing files”
wget -O output_file -q https://checkip.amazonaws.com -P DESTINATION -O output_file: benutze Minuszeichen “-“ statt output_file wenn output direkt in Terminal erscheinen soll; -q für quiet; -P für Zielordner
torsocks wget "https://cdimage.debian.org/debian-cd/current/amd64/iso-cd/debian-10.1.0-amd64-xfce-CD-1.iso" download anonymously (need to install sudo apt-get install tor torsocks), reddit
wget -A pdf,jpg -m -p -E -k -K -np http://site/path/ get all pdfs and jpgs from site
wget --accept pdf,jpg --mirror --page-requisites --adjust-extension --convert-links --backup-converted --no-parent http://site/path/ same as above using long option names
curl -s https://checkip.amazonaws.com -s für silent

gpg, apt-key

Note: Do not forget to remove the respective sources list in /etc/apt/sources.list.d/ as well.

command description
gpg –list-keys list your keys (will list only the ones stored in ~/.gnugpg, but not the ones stored in /etc/apt/trusted.gpg.d/, see stackoverflow)
gpg –delete-keys A3C4F0F979CAA22CDBA8F512EE8CBC9E886DDD89 delete key A3C4F0F979CAA22CDBA8F512EE8CBC9E886DDD89 from keyring
apt-key list  
sudo apt-key del “27B2 5BF6 36CF 72B4 334D AC98 F84C B847 29F1 B545” it is safer to use the whole fingerprint, the keyid could have duplicates (at least when you use PGP for emails, I read you should share your whole fingerprint and not just the keyid)

cron

The software utility cron also known as cron job is a time-based job scheduler in Unix-like computer operating systems. Users who set up and maintain software environments use cron to schedule jobs to run periodically at fixed times, dates, or intervals.

command description
crontab -e opens a file in which jobs can be specified (read this file for more info)

network

socket statistics

“socket” (aka the 2-Tuple (IP, Port), see DatKom.md)

command description
netstat -tulpn \| grep ':80' check if port :80 is in use
sudo netstat -lpn \| grep :8889 zeigt pid des Prozesses auf port 8889 (port kann dann mit kill \<pid\> frei gemacht werden)
ss ss is the new netstat (ss is faster, more human-readable and easier to use); displays stats for PACKET, TCP, UDP, DCCP, RAW, and Unix domain sockets, linux.com

Download, Upload

command description
md5sum file to check if the file file is not corrupted after transferring it (check if the md5sum is the same on both sides of the file transfer)

ssh

command description
w list all ssh sessions
enter ~ . disconnect (when frozen), see man ssh, stackoverflow
ssh bra-ket@10.14.14.60 installiere vorher openssh-server auf beiden Computern
firefox -no-remote -no-xshm display firefox on local client (no -X or -Y flag needed in previous ssh command)

Achtung:

  • erst in den Server einloggen und dann erst in den Computer einloggen, der die Internetverbindung des Servers benutzt !
  • Error: “X11 connection rejected because of wrong authentication.”
    • ~/.Xauthority löschen und nochmal per ssh einloggen kann helfen bei xauth Problemen (siehe issue) !
    • (prüfe evtl noch) nach source:
      • Make sure X11 SSHD Forwarding Enabled
      • Make sure X11 client forwarding enabled

Graphics/Display

command description
ssh -Y bra-ket@10.14.14.60 display graphical output on trusted local client (Caution: may lead to security issues), difference -X vs -Y flag
ssh -X bra-ket@10.14.14.60 display graphical output on untrusted local client, difference -X vs -Y flag
export DISPLAY=localhost:10.0 set display (use w or xauth list to list diplays) (“:0” ist der server monitor; zB. “localhost:10.0” ist der client monitor, wobei localhost:=127.0.0.1 (127.0.0.1 is the loopback Internet protocol (IP) address also referred to as the localhost. The address is used to establish an IP connection to the same machine or computer being used by the end-user. The same convention is defined for computers that support IPv6 addressing using the connotation of ::1.)

On Macs

command description
caffeinate -u for Mac: prevent the system from sleeping and (-u for) prevent the system from sleeping source

ssh keys

command description
ssh-keygen -R 10.14.14.92 remove 10.14.14.92 from .ssh/known_hosts (falls aus Versehen geaddet)

scp

Achtung: Spaces müssen im path DOPPELT escapet werden ! (s. hier)

command description
scp "source" "target" immer Anführungszeichen " um den source Pfad setzen!
scp -rv Macbook:"~/Desktop/Uni/FS1/Essential\ Astrophysics\ WS1819" ~/Desktop/ spaces DOPPELT escapen (hier: mit " UND mit \ gleichzeitig)
scp -r [!.]* source target exclude hidden files

rsync

rsync basics

Rsync patterns: stackexchange

command description
rsync -a path/to/source/ path/to/destination/ copy directory; note: always use / at the end of the path/to/source/ (Warning: -a better than -r because -r tag does not copy some stuff, e.g. symlinks)
rsync -avz *source* *destination* -z flag: compressing and transfer the files (comes in handy while transferring a huge amount of data over a slow internet connection)
rsync -av --progress show progress report

rsync exclude

command description
rsync -a --exclude="SomeDirForPythonInstall" exclude directory SomeDirForPythonInstall
rsync -a --exclude=".*" excludes hidden files and directories
rsync -a --exclude=".*/" exclude hidden directories only
rsync -av --progress sourcefolder /destinationfolder --exclude thefoldertoexclude exclude thefoldertoexclude
rsync -av --progress sourcefolder /destinationfolder --exclude thefoldertoexclude --exclude anotherfoldertoexclude you can use -exclude multiple times (stackoverflow)
rsync -av --progress ../../kitcar-gazebo-simulation/ ./kitcar-gazebo-simulation/ --exclude '*.bag' exclude all files ending with .bag in the current directory, no recursive traversal (patterns)

Resume partially scp-transferred files using Rsync

source

command description
rsync -P -rsh=ssh ubuntu.iso sk@192.168.225.22:/home/sk/ resume partially transferred file ubuntu.iso
rsync --partial -rsh=ssh ubuntu.iso sk@192.168.225.22:/home/sk/ see above
rsync -avP ubuntu.iso sk@192.168.225.22:/home/sk/ see above
rsync -av --partial ubuntu.iso sk@192.168.225.22:/home/sk/ see above

tree

command description
tree -H ./ > result.html save directory tree to file
tree -aH --du -h ./ > result.html report human readable sizes of files and folders
tree -aJ --du -h ./ > result.json output json format
firefox ./result.html view html tree created by tree command

xmodmap, xev

Deprecated, use setxkbmap instead.

Use

xev

to find the keycode of a key. Then, in order to remap this key, run e.g.

# Syntax: xmodmap -e "keycode [keyNumber] = [normal] [shift] [NoIdea] [NoIdea] [altGr] [shift+altGr]"
xmodmap -e "keycode 48 = bracketright braceright NoSymbol NoSymbol adiaeresis Adiaeresis"
xmodmap -e "keycode 47 = bracketleft braceleft NoSymbol NoSymbol odiaeresis Odiaeresis"
xmodmap -e "keycode 45 = 0x06b 0x04b"

Note: You can look up [keyNumber] under keysymdef.h.

Alternatively, create:

# .Xmodmap in $HOME/ directory

keycode 47 = bracketleft braceleft NoSymbol NoSymbol odiaeresis Odiaeresis
keycode 48 = bracketright braceright NoSymbol NoSymbol adiaeresis Adiaeresis

then in your .bashrc add

xmodmap ~/.Xmodmap

This will load these maps automatically after reboot.

TODO: The xmodmap ~/.Xmodmap in your .bashrc is executed every time a new terminal instance is launched which is bad for terminal startup time. Find another solution.