bash / sh cheatsheet

Basic

Cut specific column output

$0 will get the whole line, $n will get the n'th column

ls -l | awk '{print $2}'

If delimiter is predictable, can also use cut

date | cut -d' ' -f4

Loop over range

for i in {1..255}; do nc -cv 10.100.56.$i 22; done

Loop over list in file

cat list.txt | while read line; do echo "$line"; done

while read line; do echo "$line"; done < list.txt

Generate Random String

tr -dc a-zA-Z0-9 < /dev/random | head -c 18

Complex

Loop over output

for i in $(docker images | grep "2 days ago" | awk '{print $3}'); 
  do docker image rm -f $i; 
done