au233-Unit 1 (2)

shell job control: jobs -l|-n|-p

fg :foreground

bg :background

kill %(n) :n=job number

Ctrl -Z :suspend job

Command Substitution

var=`command` or var=$(command)

Unit 2 : Variables

readonly var1=xxx

positional parameters: set arg1 arg2

variable parameters：$#,$@,$*

Ctrl-D : return to main shell