General

Run the same command multiple times with different parameters

for i in a b c; do command $i; done

You can use different kind of lists to iterate:

  • 1 2 3 4 5
  • $(Linux-Or-Unix-Command-Here)
  • {1..5}

Reference: nixCraft - Bash For Loop Examples

Image manipulation

join multiple images into one single pdf [needs imagemagick]
convert 1.png 2.png out.pdf

join pdfs into a single file with pdftk
pdftk file1.pdf file2.pdf file3.pdf cat output newfile.pdf

change resolution/size of a pdf
gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dPDFSETTINGS=/printer -dNOPAUSE -dQUIET -dBATCH -sOutputFile=output.pdf input.pdf

Parameters:
dPDFSETTINGS=/value , where values is the quality of conversion:

  • screen (screen-view-only quality, 72 dpi images)
  • ebook (low quality, 150 dpi images)
  • printer (high quality, 300 dpi images)
  • prepress (high quality, color preserving, 300 dpi imgs)
  • default (almost identical to /screen)

Read the docs for more info about available parameters.

scale a PDF with pdfjam
pdfjam --a4paper --noautoscale true --scale .71

sips – scriptable image processing system [Only in MacOS]
Scale an image (preserve ratio) to a specific size
sips -Z 128 image.png --out output.png

Convert to another format
sips -s format png icon.icns --out icon.png
sips -s format icns icon.png --out icon.icns

convert from PPT to PDF using Libreoffice
libreoffice --headless --invisible --convert-to pdf *.ppt

small script to join images (inside the same folder and named with a pattern) into a single pdf

read -p "Find: " find  
read -p "Output: " output
find . -name "$find*" | sort -n | sed 's/\ /\\ /g' | tr '\n' ' ' | sed 's/$/\ '$output'.pdf/' | xargs convert -compress jpeg
Diff with colors

if you want to diff two files and get colors like you get when using git diff you can use this:
git diff --no-index file1 file2

Time/Data manipulation

Get yesterday date: date -d "yesterday 13:00" '+%Y-%m-%d'

SSH

Execute a multi-line script via ssh 
cat << 'EOF' | ssh user@host
command-1
command-2
command-3
EOF
Jump Hosts – Passing through a gateway or two using ssh

When port forwarding is available the easiest way is to use ProxyJump in the configuration file or -J as a run-time parameter. (Of course you may also use the ProxyCommand ssh(1) option to invoke the netcat utility.)
An example of -J usage is: ssh -J firewall.example.org:22 server2.example.org
Ref: OpenSSH/Cookbook/Proxies and Jump Hosts

Tags: cheatsheet ssh bash