# grep strings recursiv
> grep -Ri 'foo' ~/path

# grep strings recursiv using regex
> grep -REi 'foo.*' ~/path

# exclude lines starting with a #
> grep -v '#' ~/file
> grep -E '^[^#]'

# cut first digit on every line
> sed 's/^.\{,1\}//' ~/file

# determine the state of a TCP/UDP port on a remote host
> nc -zv w.x.y.z 1194
> nc -zvu w.x.y.z 1194

# list files by modification time
> ls -1t ~/path

# show the most recent file in a directory
> ls -1t ~/path | tail -1

# for loop
> for i in '~/path/*.rar'; do unrar x -pPASSWORD -o- '$i'; done

# adding date to file name
> touch foobar-$(date +%Y-%m-%d)

# adding date + time to file name
> touch foobar-$(date +%Y-%m-%d-%H%M%S)

# testing mail
> echo "Testing mail setup" | mail -s "Test email from `hostname`" foo@example.com

# testing mail, spoof sender
> echo "Testing mail setup" | mail -r foo@example.com -s "Test email from `hostname`" bar@example.com

# bash math
> ((x=1028*6))|echo $x

# python webserver
> python3 -m http.server -port 9999 -d ~/path

# rsync options
> rsync -rvzP -e 'ssh -p2222 -I /usr/lib/opensc-pkcs11.so' foo@bar:/foobar ~/foobar