Notes

Appearance

Bash Snippets ​

General ​

  1. Find difference in output of two shell commands:

    bash
    diff <(ls) <(ll)

# or to see all the difference similar to (n)vim -d (diff)
nvim <(pacman -Qi nvim) <(pacman -Si nvim)

  2. Upload files and share for free (limit 10GB):

    bash
    curl --upload-file ./hello.txt https://transfer.sh/hello.txt

  3. Translate or delete characters:

    bash
    echo $PATH
# /home/prabhu/.local/bin:/usr/local/sbin

echo $PATH | tr ':' '\n'
# /home/prabhu/.local/bin
# /usr/local/sbin

  4. Columnate lists:

    bash
    mount | column -t

Arch Webcam Setup

Images ​

  • Compress image:

    bash
    magick -format jpg -quality 50 /path/to/image.svg /path/to/image.jpg

# or

mogrify -compress JPEG -quality 50 /path/to/image.jpg

# or

convert -strip -interlace Plane -gaussian-blur 0.05 -quality 85% /path/to/source/image.jpg /path/to/result/image.jpg

# or

jpegoptim --size=512k /path/to/image.jpg

  • Compare images: using Image magick compare

    bash
    magick compare image1.jpg image2.jpg diff.png

7z ​

  • 7z with ultra compression:

    bash
    7z a -t7z -m0=lzma -mx=9 -mfb=64 -md=32m -ms=on archive.7z dir1

PDF ​

  • PDF to image:

    bash
    # pdftoppm <image_format> <input_pdf> <image_output>

pdftoppm -png resume.pdf resume.png

# by default it will output 100 DPI, which can be increased
pdftoppm -png -rx 300 -ry 300 resume.pdf resume.png

ffmpeg ​

  • Simple conversion of videos:

    bash
    ffmpeg -i input.mp4 output.mp4

ffmpeg documentation

mpv ​

Use mpv to take snapshots from webcam:

bash
mpv av://v4l2:/dev/video0 --profile=low-latency --untimed

To use MJPEG as the pixelformat instead of the default, which in most cases is YUYV, you can run the following instead:

bash
mpv --demuxer-lavf-format=video4linux2 --demuxer-lavf-o-set=input_format=mjpeg av://v4l2:/dev/video0

In some cases this can lead to drastic improvements in quality and performance (5 FPS -> 30 FPS for example), see the mpv documentation

Python ​

pip ​

  • pip batch update:

    bash
    pip install -U `pip list --outdated | tail -n +3 | awk '{print $1}'`

Manjaro ​

Pacman ​

  • List all installed packages sorted by size:

    bash
    pacman -Qi | awk '/^Name/{name=$3} /^Installed Size/{print $4$5, name}' | sort -h

  • Clear pacman cache

    bash
    # get total cached packages
sudo ls /var/cache/pacman/pkg/ | wc -l

# get total cache size
du -sh /var/cache/pacman/pkg/

# clean all packages, expect the 3 most recent versions
sudo paccache -r

# clean all packages, expect the n most recent versions
sudo paccache -rk n

# remove all uninstalled packages
sudo paccache -ruk0

# OR
sudo pacman -Sc

# remove all installed and uninstalled package cache
sudo pacman -Scc

  • Alternative create a hook to auto clean cache

    bash
    sudo vi /etc/pacman.d/hooks/clean_package_cache.hook
    text
    [Trigger]
Operation = Upgrade
Operation = Install
Operation = Remove
Type = Package
Target = *
[Action]
Description = Cleaning pacman cache...
When = PostTransaction
Exec = /usr/bin/paccache -r

Refer: Recommended ways to clean cache

Starship Prompt ​

Starship is a minimal, blazing-fast, and infinitely customizable cross-shell prompt for any shell

Installation Linux ​

  1. Install/Update the latest version:

    bash
    curl -sS https://starship.rs/install.sh | sh

  2. Add the following to the end of ~/.bashrc or ~/.zshrc:

    bash
    eval "$(starship init bash)"
# -- or --
eval "$(starship init zsh)"

OpenSSH ​

Known Hosts

  • Remove Entry from the Known-Hosts File:
bash
ssh-keygen -R hostname

Using the SSH Config File

If you are regularly connecting to multiple remote systems over SSH, you can configure your remote servers with the .ssh/config file

Example:

ini
Host dev
    HostName dev.your-domain
    User xcad
  Port 7654
    IdentityFile ~/.ssh/targaryen.key
Host *
    User root
    Compression yes

Connect to a host (like dev , eg.) with ssh dev

OpenSSL ​

  • Generate a DKIM private and public keypair:
bash
openssl genrsa -out dkim_private.pem 2048

openssl rsa -in dkim_private.pem -pubout -outform der 2>/dev/null | openssl base64 -A

KDE ​

Baloo File Indexer ​

  • Disable it

    bash
    balooctl suspend
balooctl disable