; ===========================
; NIXOS
; ===========================

% nixos
# Rebuild a flake system derivation
sudo nixos-rebuild <type> --flake .#<flake>
$ type: echo -e "switch\nbuild\nboot"
$ flake: echo -e "nixinator\nnixtop"

% nixos
# Find out why a package is included in the closure when building the system derivation
nix why-depends /run/current-system nixpkgs#<package>

% nixos
# Find the storepath of an executable in the users path
readlink -f $(which <executable>)
$ executable: bash -c "compgen -c"

% nixos
# Find the wanted dynamic libraries of an executable in the users path
ldd $(readlink -f $(which <executable>))
$ executable: bash -c "compgen -c"

; ===========================
; SYSTEMD
; ===========================

% systemd
# List failed system units
sudo systemctl --failed

% systemd
# List failed user units
systemctl --user --failed

% systemd
# List system errors
sudo journalctl -p 3 -xb

% systemd
# List kernel errors
sudo journalctl -p 3 -xb -k

% systemd
# List system unit errors
sudo journalctl -xb --unit=<unit>
$ unit: sudo systemctl list-units --type=service --all --full --no-pager --legend=false --plain | awk -F' ' '{print $1}'

% systemd
# List user unit errors
journalctl -xb --unit=<unit>
$ unit: systemctl --user list-units --type=service --all --full --no-pager --legend=false --plain | awk -F' ' '{print $1}'

; ===========================
; SHELL
; ===========================

% shell
# Launch a detached process with suppressed output
<command> &>/dev/null &; disown

% shell
# Generate a large text file
yes "The quick brown fox jumps over the lazy dog" | head -c <size> > <output>

% shell
# For-loop in fish shell
for o in <objects>; <action>; end

% shell
# Find files larger or smaller than a specified size in the current directory
fd --type file --size <mode><size> -- "<regex>" .
$ mode: echo -e "+\t\tFind Larger Files\n-\t\tFind Smaller Files" --- --column 1

% gdu
# Visualize storage usage on all mounted disks
sudo gdu -d

% duf
# List all mounted devices
sudo duf

% duf
# Display INode information of all mounted devices
sudo duf -inode

% awk
# Select a column
awk -F<separator> '{print $<print>}'
$ separator: echo -e "' '\t\tWhitespace\n'[ ]'\t\tSingle Space\n'\\\t'\t\tTabs" --- --column 1

% mime
# Determine the mime-type of a file
file --mime-type <file>
$ file: eza -f -1

% mime
# Query the default app for a mime type
xdg-mime query default <mimetype>

% mime
# Query the default app for a file
xdg-mime query default $(file --mime-type <file> | awk -F' ' '{print $2}')
$ file: eza -f -1

; ===========================
; CODE
; ===========================

% code
# Disassemble an object file
objdump -d -S -M <arch>,<syntax> "<file>" | bat -l nasm
$ arch: echo -e "x86-64\t\t64 Bit\ni386\t\t32 Bit\ni8086\t\t16 Bit" --- --column 1
$ syntax: echo -e "intel\t\tIntel Syntax\natt\t\tAT&T Syntax" --- --column 1
$ file: eza -f -1

; ===========================
; DOCS
; ===========================

% docs
# Extract svg figure from pdf page
pdftocairo -f <page> -l <page> -svg "<input>" "<output>"
$ input: eza -f -1

; ===========================
; YT-DLP
; ===========================

% yt-dlp
# Download mp4 video in best quality
yt-dlp -f 'bv*[ext=mp4]+ba[ext=m4a]/b[ext=mp4] / bv*+ba/b' --recode-video mp4 "<url>"

% yt-dlp
# Download mp3 video in best quality
yt-dlp -f 'ba' --extract-audio --audio-format mp3 "<url>"

; ===========================
; FFMPEG
; ===========================

% ffmpeg
# Create a slow motion version of a video with interpolated/blended frames
ffmpeg -i "<input>" -filter:v "minterpolate='mi_mode=mci:mc_mode=aobmc:vsbmc=1:fps=<doublefps>',setpts=2*PTS" output.mp4
$ input: eza -f -1

% ffmpeg
# Detect black bar dimensions automatically by looking at the first 10 frames
ffmpeg -i "<input>" -vframes 10 -vf cropdetect -f null -
$ input: eza -f -1

% ffmpeg
# Preview video with applied crop settings
ffplay -vf crop=<width>:<height>:<x>:<y> "<input>"
$ input: eza -f -1

% ffmpeg
# Re-encode the video with applied crop settings
ffmpeg -i "<input>" -vf crop=<width>:<height>:<x>:<y> -c:a copy output.mp4
$ input: eza -f -1

% ffmpeg
# Reencode and compress the video using the h265 codec
ffmpeg -i "<input>" -vcodec libx265 -crf <quality> "out_<input>"
$ input: eza -f -1
$ quality: echo -e "24\n25\n26\n27\n28\n29\n30\n"

% ffmpeg
# Reencode and compress multiple videos using the h265 codec
fish -c "for name in <files>; ffmpeg -i '$name' -vcodec libx265 -crf <quality> 'out_$name'; end"
$ quality: echo -e "24\n25\n26\n27\n28\n29\n30\n"