$a="W.endy.chen.SHAO"
$b=$a.Substring(0,$a.Length-5) -replace "\.","_"
$c=$a.Substring(0,$a.Length-5).Replace(".","_")
$d=($a.substring(0,$a.Length-5)) -replace "\.(?!.*\.)","_"
#只替换最后一个.为_,其他.保持不变
echo $a,$b,$c,$d
结果:
W.endy.chen.SHAO
W_endy_chen
W_endy_chen
W.endy_chen