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Useful commands

ImageMagick

Overlay 2 images with transparency

magick convert bottom.png ( top.png -alpha set -channel a -evaluate set 75% +channel ) -gravity center -compose over -composite out.png magick composite -dissolve 75 -gravity Center top.png bottom.png -alpha Set out.png

Convert all JPGs to PNG & Remove

for f in *.jpg; do magick convert "$f" -quality 100 -format png "${f/.jpg/.png}" && rm "$f"; done

Convert all WEBPs to PNG

for f in *.webp; do magick convert "$f" "${f/.webp/.png}"; done

Resize images

for f in *.png; do magick convert "$f" -quality 100 -filter Lanczos -resize 1080x1350 "${f/.png/-lg.png}"; done

Crop image

magick convert input.png -crop 800x600+100+50 output.png

Add border to image

magick convert input.png -bordercolor black -border 10x10 output.png

Create thumbnail

magick convert input.png -thumbnail 200x200 thumb.png

Batch rename files with counter

i=1; for f in *.png; do mv "$f" "image_$(printf %03d $i).png"; ((i++)); done

FFmpeg

Trim video

ffmpeg -accurate_seek -ss 00:00:07.5 -i source.mp4 -c:v copy -c:a copy out.mp4

Split video into frames

ffmpeg -i video.mp4 -framerate 25 video/%04d.png

Merge frames into video (muted)

ffmpeg -framerate 25 -i frames/%04d.png -c:v libx264 -crf 7 -pix_fmt yuv420p -y muted.mp4

Copy sound from another video

ffmpeg -i muted.mp4 -i original.mp4 -c:v copy -map 0:v:0 -map 1:a:0 -y out.mp4

Extract audio from video

ffmpeg -i video.mp4 -vn -acodec libmp3lame -q:a 2 audio.mp3

Compress video

ffmpeg -i input.mp4 -vcodec libx264 -crf 28 output.mp4

Rotate video 90 degrees clockwise

ffmpeg -i input.mp4 -vf "transpose=1" output.mp4

Add watermark to video

ffmpeg -i video.mp4 -i watermark.png -filter_complex "overlay=10:10" output.mp4

Network

Test port connectivity

nc -zv hostname 80

Find process using a port

lsof -i :8080

Download file with progress

curl -L -o filename.zip https://example.com/file.zip

Test DNS resolution

dig example.com

System

Find large files

find / -type f -size +100M 2>/dev/null

Create compressed archive

tar -czf archive.tar.gz directory/

Extract tar.gz archive

tar -xzf archive.tar.gz

Find files modified in last 7 days

find . -type f -mtime -7

Text Processing

Replace text in files

sed -i 's/old/new/g' file.txt

Extract column from CSV

awk -F',' '{print $3}' data.csv

Count lines in file

wc -l file.txt

Remove duplicate lines

sort file.txt | uniq

Find and replace in multiple files

find . -type f -name "*.txt" -exec sed -i 's/old/new/g' {} +

Merge lines with paste

paste -sd ',' file.txt

Process Management

Kill process by name

pkill -f process_name

List all processes with memory usage

ps aux --sort=-%mem | head -n 10

Run command in background

nohup command &

List background jobs

jobs -l

File Operations

Find and delete files

find . -name "*.tmp" -type f -delete

Change file permissions recursively

find . -type f -exec chmod 644 {} ; find . -type d -exec chmod 755 {} ;

SSH & Remote

Copy SSH key to server

ssh-copy-id user@hostname

SSH tunnel (port forwarding)

ssh -L 8080:localhost:80 user@hostname

Run command on remote server

ssh user@hostname 'command'

SCP with compression

scp -C file.txt user@hostname:/path/