get-alias -definition get-childitem   #dir的别名为get-childitem

#只列出目录
dir | where-object {$_ -is [System.IO.DirectoryInfo]}
dir | where-object {$_.PSIsContainer}
dir | where-object {$_.Mode.Substring(0,1) -eq "d"}
#只列出文件
dir | where-object {$_ -is [System.IO.FileInfo]}
dir | where-object {$_.PSIsContainer -eq $false}
dir | where-object {$_.Mode.Substring(0,1) -ne "d"}