系统技术非业余研究

这是未公开的一个特性, 很方便查看Erlang内部的port使用状态.

演示下:

root@ubuntu:~# erl
Erlang R13B04 (erts-5.7.5) [source] [smp:2:2] [rq:2] [async-threads:0] [hipe] [kernel-poll:false]

Eshell V5.7.5  (abort with ^G)
1> 
BREAK: (a)bort (c)ontinue (p)roc info (i)nfo (l)oaded
       (v)ersion (k)ill (D)b-tables (d)istribution
o
=port:#Port<0.1>
Slot: 1
Connected: <0.3.0>
Links: <0.3.0>
Port controls linked-in driver: efile
=port:#Port<0.49>
Slot: 49
Connected: <0.18.0>
Links: <0.18.0>
Port controls linked-in driver: efile
=port:#Port<0.306>
Slot: 306
Connected: <0.21.0>
Links: <0.21.0>
Port is UNIX fd not opened by emulator: 2/2
=port:#Port<0.315>
Slot: 315
Connected: <0.23.0>
Links: <0.23.0>
Port controls linked-in driver: tty_sl -c -e