Find who is logged on and What they are doing

$ w
 10:11:28 up 14 days,  2:33,  1 user,  load average: 0.00, 0.00, 0.00
USER     TTY      FROM             LOGIN@   IDLE   JCPU   PCPU WHAT
asis     pts/0    XXX.XXX.XXX.XXX  10:11    0.00s  0.05s  0.01s w

Kill tty Connections

$ pkill -9 -t <TTY>

# Example
$ pkill -9 -t pts/0

Find Common Elements Between Two Lists

comm is great, but indeed it needs to work with sorted lists.

$ comm -12  <(ls one) <(ls two)

Alternative with sort:

# Intersection of two lists:
$ sort <(ls one) <(ls two) | uniq -d

# Symmetric difference of two lists:
$ sort <(ls one) <(ls two) | uniq -u

reflector

$ curl "https://asispatra.github.io/vault/reflector" -o reflector
$ sudo mv reflector /usr/local/bin/
$ sudo chmod a+rx /usr/local/bin/reflector

# Usage
$ reflector <FILENAME> <NEW_FILE_NAME>