$ is_parent() { [[ "$2" =~ $1/? ]]; }

说明

扩展的函数将如下所示：

T() {
 if [["$2" =~ $1/? ]]; then
 echo"$2 is child of $1"
 return 0
 else
 echo"$2 is NOT child of $1 ($?)"
 return 1
 fi
}