Terminal control characters and signals

Caret notation is a notation for control characters in ASCII. The notation assigns ^A to control-code 1, sequentially through the alphabet to ^Z assigned to control-code 26 (0x1A). For the control-codes outside of the range 1–26, the notation extends to the adjacent, non-alphabetic ASCII characters.

Source

^C - SIGINT - interrupt signal - default behaviour is to terminate the process, can be caught or ignored, see trap, intention is to shutdown gracefully

^\ - SIGQUIT - dump core signal - user initiated terminate, but not so graceful

^Z - SIGSTOP - pause - shells use this to implement job control - send to background

 djen at xps in ~
 $ sleep 100
 ^Z
 [1]+  Stopped                 sleep 100
 djen at xps in ~
 $ jobs
 [1]+  Stopped                 sleep 100
 djen at xps in ~
 $ bg 1
 [1]+ sleep 100 &
 djen at xps in ~
 $ fg 1
 sleep 100
 ^C

^D - EOF

 djen at xps in ~
 $ cat
 send ^+D after this line
 send ^+D after this line

SIGKILL - process can't trap this, it cannot cleanup, and thus this is a signal of last resort.

 djen at xps in ~
 $ sleep 100
 ^Z
 [1]+  Stopped                 sleep 100
 djen at xps in ~
 $ jobs -l
 [1]+ 45817 Stopped                 sleep 100
 djen at xps in ~
 $ kill -9 45817
 djen at xps in ~
 $ jobs -l
 [1]+ 45817 Killed                  sleep 100

SIGTERM vs SIGINT?

ttyUSB vs ttyACM

What is the difference between /dev/ttyUSB and /dev/ttyACM?