LSTR命令画出的直线只能是直的，对应GUI命令Straight Line
L命令可以画曲线，通过指定起点和终点的斜率，对应GUI命令In Active Coord

LSTR命令
Defines a straight line from P1 to P2 using the global Cartesian coordinate system. The active coordinate system will be ignored. The line shape is invariant with the coordinate system after it is generated. Lines may be redefined only if not yet attached to an area.
L命令
Defines a line between two keypoints from P1 to P2. The line shape may be generated as "straight" (in the active coordinate system) or curved. The line shape is invariant with coordinate system after it is generated. Note that solid modeling in a toroidal coordinate system is not recommended. A curved line is limited to 180°. Lines may be redefined only if not yet attached to an area.
不同点是一个是
The active coordinate system will be ignored. 与激活的坐标系无关，不管是柱坐标系，笛卡尔坐标系，其形状还是直线
The line shape may be generated as "straight" (in the active coordinate system) or curved. 与激活的坐标系有关，如果是笛卡尔坐标系则为直线，如果是柱坐标系则为曲线

下面有个例子可以直观的表示其命令的差别之处：

K,1,2,,,
K,2,0,1,,
CSYS,1  
l,1,2   
lstr,1,2