sample session related to “command expansion” in Bash shell

$a=`time` real 0m0.000s user 0m0.000s sys 0m0.000s $a bash: a: command not found $a=`ls` $a bash: a: command not found $echo a a $echo $a a.txt b.txt trueangle $echo `a` bash: a: command not found $a=`ls` $b=time $echo $b time $b=`time` real 0m0.000s user 0m0.000s sys 0m0.000s $echo $b $b=`time` real 0m0.000s user 0m0.000s sys …