$($_.)作用
1 $a=get-process 2 foreach ($b in $a) 3 { 4 write-host "hello: $($b.id)" 5 }
返回结果：
hello: 2536
hello: 3528
hello: 2316
hello: 608
hello: 732
hello: 1392
hello: 2456
hello: 2680
hello: 5940
hello: 3540
1 $a=get-process 2 foreach ($b in $a) 3 { 4 write-host "hello: $b.id" 5 }
返回结果：
hello: System.Diagnostics.Process (vmware-tray).id
hello: System.Diagnostics.Process (vmware-usbarbitrator64).id
hello: System.Diagnostics.Process (wininit).id
hello: System.Diagnostics.Process (winlogon).id
hello: System.Diagnostics.Process (wlanext).id
hello: System.Diagnostics.Process (WmiPrvSE).id
hello: System.Diagnostics.Process (WmiPrvSE).id
hello: System.Diagnostics.Process (WmiPrvSE).id
hello: System.Diagnostics.Process (wmpnetwk).id
