Computer Stuff, guide h

• utils - basename - mv - tree - sed
• imagemagick- ffmpeg- sshfs- tmux

lot's to do, sorry for the mess unix join() cmp()

utils

basename

echo "/path/to/file1 /another/path/file2" | xargs -n1 basename

chown

chown -R dawn:wheel .

Changes user and group owenership

mv

Move files from a directory into current directory

mv directory/* .

tree

Generate sitemap

tree -H ./ > sitemap.html

tree displays the directory structure of the current directory. -d option displays only directories. -I option allows to exclude directories that match specific pattern e.g.

tree -I node_modules

In order to exclude multiple directories at once, their names must be separated by | sign, i.e.

tree -I 'node_modules|cache|test_*'

This command will skip node_modules, cache directories (along with their content) from the output, and all directories that match test_* wildcard expression.

sed

Removing all instances of the "<" sign

sed -i 's/>//g' yourfile.md

• -i tells sed to edit the file, rather than output modified text to standard outputA
• s stands for substitution
• // The replacement string is between the second and third slashes. Since there is nothing between these slashes, sed replaces > with nothing
• g stands for global, replacing every instance

Change all instances of a string

sed -i 's/webp/avif/g' filename

Creates backup

sed -i.bak 's/webp/avif/g' filename

Remove the pattern "../"

sed -i 's/\.\.\///g' filename.html

Misc

sed -i 's/\<str\>/gif/g' filename.html

s/<str>/gif/g: Substitute (s) str with gif, where < and > ensure that only the exact word str is replaced, not occurrences where str is a part of another word.

@

Loop

for file in *.md; do sed -i 's|\.pix/||g' "$file"; done

removes every instance of .pix/

sed 's/="./="/' filename

sed 's/.md//g' filename

ghostscript

gs -dSAFER -dBATCH -dNOPAUSE -sDEVICE=pngalpha -r300 -sOutputFile=output-PERCENTSIGNd.png input.pdf

git

Create new repository

git init

git add .

git commit -m "Commit Message"

git branch -M main

git remote add origin git@github.com:username/repo-name.git

git push -u origin main

Generate new SSH key

ssh-keygen -t ed25519 -C "your_email@example.com"

If you are using a legacy system that doesn't support the Ed25519 algorithm, use:

ssh-keygen -t rsa -b 4096 -C "your_email@example.com"

imagemagick

todo

convert -background none -fill black -pointsize 48 label:"c@avsbq.org·" -virtual-pixel none -distort Arc 360 avsemail.pn

Remove Whitespace

convert -trim

Flip images

To flip horizontally

convert input.jpg -flip output.jpg

To flip vertically

convert input.jpg -flop output.jpg

Dithering

convert tux.webp -resize 384 -dither FloydSteinberg -remap pattern:gray50 tux.webp

Ordered

convert invader.webp -colorspace gray -ordered-dither o8x8 invader2.webp

Rotate

Anti-clockwise

convert dumbbell.jpg -rotate -90 dumbbell1.jpg

Clockwise

Same command as before but! omit the - before 90

Add spiral to image

convert -background none -fill black -pointsize 48 label:"you@email.com" -virtual-pixel none -distort Arc 360 output.png

ffmpeg

For delay

ffmpeg -i a.mp4 -itsoffset 2 -i a.m4a -c:v copy -c:a aac -strict experimental b.mp4

Combine video and audio

ffmpeg -i a.mp4 -i a.m4a -c:v copy -c:a aac -strict experimental b.mp4

converting videos

ffmpeg -i a.mkv -codec copy a.mp4

SSHFS

From local machine

sudo sshfs root@avsbq.org:/var/www/werc/sites/ /mnt/avsbq.org

to debug use

-o debug

Remove offending key

ssh-keygen -R avsbq.org

mpv

mpv -vf=hflip /dev/video0