Operation Manual

The special shell variable $$, whose value is the process ID of the shell, has been used.
The command lsof lists all the les currently open when used without any parameters.
There are often thousands of open les, therefore, listing all of them is rarely useful.
However, the list of all les can be combined with search functions to generate useful
lists. For example, list all used character devices:
tux@mercury:~> lsof | grep CHR
bash 3838 tux 0u CHR 136,0 2 /dev/pts/0
bash 3838 tux 1u CHR 136,0 2 /dev/pts/0
bash 3838 tux 2u CHR 136,0 2 /dev/pts/0
bash 3838 tux 255u CHR 136,0 2 /dev/pts/0
bash 5552 tux 0u CHR 136,5 7 /dev/pts/5
bash 5552 tux 1u CHR 136,5 7 /dev/pts/5
bash 5552 tux 2u CHR 136,5 7 /dev/pts/5
bash 5552 tux 255u CHR 136,5 7 /dev/pts/5
X 5646 root mem CHR 1,1 1006 /dev/mem
lsof 5673 tux 0u CHR 136,5 7 /dev/pts/5
lsof 5673 tux 2u CHR 136,5 7 /dev/pts/5
grep 5674 tux 1u CHR 136,5 7 /dev/pts/5
grep 5674 tux 2u CHR 136,5 7 /dev/pts/5
When used with -i, lsof lists currently open Internet les as well:
tux@mercury:~> lsof -i
[...]
pidgin 4349 tux 17r IPv4 15194 0t0 TCP \
jupiter.example.com:58542->www.example.net:https (ESTABLISHED)
pidgin 4349 tux 21u IPv4 15583 0t0 TCP \
jupiter.example.com:37051->aol.example.org:aol (ESTABLISHED)
evolution 4578 tux 38u IPv4 16102 0t0 TCP \
jupiter.example.com:57419->imap.example.com:imaps (ESTABLISHED)
npviewer. 9425 tux 40u IPv4 24769 0t0 TCP \
jupiter.example.com:51416->www.example.com:http (CLOSE_WAIT)
npviewer. 9425 tux 49u IPv4 24814 0t0 TCP \
jupiter.example.com:43964->www.example.org:http (CLOSE_WAIT)
ssh 17394 tux 3u IPv4 40654 0t0 TCP \
jupiter.example.com:35454->saturn.example.com:ssh (ESTABLISHED)
13.2.6 Kernel and udev Event Sequence
Viewer: udevadm monitor
udevadm monitor listens to the kernel uevents and events sent out by a udev rule
and prints the device path (DEVPATH) of the event to the console. This is a sequence
of events while connecting a USB memory stick:
184 Reference