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AutoLISP 1.03 - Custom AutoCAD Commands and Asking Questions

AutoLISP and Visual LISP programs can be used to custom AutoCAD commands.

 

Executing an AutoCAD Commands in LISP

Syntax - (command [arguments] ...)

 

The command function evaluates each argument and sends it to AutoCAD in response to successive prompts. It submits command names and options as strings, coordinate points as a list of reals (2D points as 2 reals and 3D points as 3 reals).

LISP Example to type at AutoCAD command prompt -

    (setq PT1 (list 1.0 1.0))                    ;set start point

    (setq PT2 (list 2.0 2.0))                    ;set end point

    (command "LINE" PT1 PT2 "")   ;issue LINE command to AutoCAD, draw from PT1 to PT2, "" ends LINE command

If you needed a line drawn for 3 points you would have to

    (setq PT3 (list 3.0 3.0))

and change LISP  to

    (command "LINE" PT1 PT2 PT3 "")

 

To learn how to create LISP programs, type the command you would like to create at the command prompt, writing down each response you give.

 

AutoCAD command Example #1 (type at command prompt) -

    Command: CIRCLE

    Specify center point for circle or [3P/2P/Ttr (tan tan radius)]: 2P

    Specify first end point of circle's diameter: pick point
    Specify second end point of circle's diameter: pick point

LISP Program Example -

    (command "CIRCLE" "2P" PT1 PT2)    ;using previously set start and end points

 

AutoCAD command Example #2 (type at command prompt) -

    Command: CIRCLE

    Specify center point for circle or [3P/2P/Ttr (tan tan radius)]: pick point

    Specify radius of circle or [Diameter] <3.3997> 2.0

 

LISP Program Example -

    (command "CIRCLE" PT1 "2.0")     ;using previously set point and string number for radius

    or

    (command "CIRCLE" PT1 2.0)        ;using previously set point and real value for radius

 

AutoCAD command Example #3 (type at command prompt) -

    Command: -LAYER    (Note the "-" before Layer command to issue layer command without dialog box)

    Current layer: "0"
    Enter an option [?/Make/Set/New/ON/OFF/Color/Ltype/LWeight/Plot/Freeze/Thaw/LOck/Unlock/stAte]: M
    Enter name for new layer (becomes the current layer) <0>: 1
    Enter an option [?/Make/Set/New/ON/OFF/Color/Ltype/LWeight/Plot/Freeze/Thaw/LOck/Unlock/stAte]: C
    Enter color name or number (1-255): 1
    Enter name list of layer(s) for color 1 (red) <1>: 1
    Enter an option [?/Make/Set/New/ON/OFF/Color/Ltype/LWeight/Plot/Freeze/Thaw/LOck/Unlock/stAte]: LT
    Enter loaded linetype name or [?] <Continuous>: DASHED
    Enter name list of layer(s) for linetype "Continuous" <1>: 1
    Enter an option [?/Make/Set/New/ON/OFF/Color/Ltype/LWeight/Plot/Freeze/Thaw/LOck/Unlock/stAte]: enter
 

LISP Program Example -

    (command "-LAYER" "M" "1" "C" "1" "1" "LT" "DASHED" "1" "") ;the "" ends the layer command

 

Control Characters in Strings

 

AutoLISP control characters
Code	Description	Example	Returns
\\	\ character	(princ "This is 1 -\\-")	This is 1 -\-
\"	" character	(princ "This is a -\"-")	This is a -"-
\e	Escape character	(princ "1\e2")	1▐2 ;not sure of this usage
\n	Newline character	(princ "Line 1\nLine 2")	Line 1 Line 2
\r	Return character	(princ "12345\r")	12345 then cursor at beginning of line
\t	Tab character	(princ "1\t2\t3\nA\tB\tC")	1   2    3 A   B   C
\nnn	Character whose octal code is nnn	(princ "\123")	S ;not sure of this usage

 

 

AutoLISP "GETxxx" Functions

AutoLISP has many "GETxxx" functions that pause for user input of the indicated type and returns the value of the same type entered. This is the method used to allow users to input values as needed in programs.

 

Allowable input to the GETxxx user-input functions
Function name	Type of user input	User presses ENTER, Returns
getint	An integer value on the command line	nil
getreal	A real or integer value on the command line	nil
getstring	A string on the command line	""
getpoint	A point value on the command line or selected from the screen	nil
getcorner	A point value (the opposite corner of a box) on the command line or 2 selected point from the screen	nil
getdist	A real or integer value (of distance) on the command line or determined by selecting 2 points on the screen	nil
getangle	An angle value (in the current angle format) on the command line or based on 2 selected points on the screen	nil
getorient	An angle value (in the current angle format) on the command line or based on 2 selected points on the screen	nil
getkword	A predefined keyword or its abbreviation on the command line	""

 

GETINT

Syntax - (getint [message])

Example -

    (setq Inum (getint "\nInput Integer ? "))    ;type at command prompt

    Input #1 -

        Command: Input Integer ? 25        ;integer input

        returns: 25

    Input #2 -

        Command: Input Integer ? 25.0     ;real number input

        Requires an integer value

        Input Integer ?                                  ;allows user to re-input integer

    Input #3 -

        Command: Input Integer ? S         ;non-numeric character entered

        Requires an integer value

        Input Integer ?                                 ;allows user to re-input integer

 

Note - Values passed to getint can range from -32,768 to +32,767. If the user enters any character other than a number character, then getint displays the message "Requires an integer value," and allows the user to try again.

 

GETREAL

Syntax - (getreal [message])

Example -

    (setq Rnum (getreal "\nInput Real Number ? "))    ;type at command prompt

    Input #1 -

        Command: Input Real Number ? 25.0     ;real number input

        returns: 25.0

    Input #2 -

        Command: Input Real Number ? 25        ;Integer input

        returns: 25.0

    Input #3 -

        Command: Input Real Number ? S         ;non-numeric character entered

        Requires a numeric value

        Input Real Number ?                                 ;allows user to re-input number

 

Note - Values passed to getreal are double-precision floating-point format. If the user enters any character other than a number character, then getreal displays the message "Requires a numeric value," and allows the user to try again. Real numbers between -1 and 1 must be contain a leading zero. Real numbers can also be expressed in scientific notation (example - 4.1e-6 equals 0.0000041).

 

GETSTRING

Syntax - (getstring [cr] [message])

    [cr] = If supplied and is not nil, this will allow the user to input spaces in their input string and must be terminated by pressing ENTER. Otherwise, the input string is terminated by pressing the SPACE or ENTER keys.

 

Example #1 -

    (setq Stir (getstring "\nInput String ? "))    ;type at command prompt

    Input #1 -

        Command: Input String ? test             ;String Input

        returns: "test"

    Input #2 -

        Command: Input String ? 25.0            ;Numeric Input

        returns: "25.0"

    Input #3 -

        Command: Input String ? 25               ;Numeric Input

        returns: "25"

    Input #4 -

        Command: Input String ? C:\temp\    ;folder path input

        returns: "C:\\temp\\"

 

Example #2 -

    (setq Stag (getstring T "\nInput String ? "))    ;type at command prompt

    Input #1 -

        Command: Input String ? this is a test             ;String Input

        returns: "this is a test"

 

Note - getstring will only return the first 132 characters in the input. If the input contains the backslash character "\", getstring converts it to two backslash characters "\\". This allows you to input folder paths.

 

GETPOINT

Syntax - (getpoint [pt] [message])

    [pt] = If supplied and is not nil, this will cause AutoCAD to show a rubberband from [pt] to current cursor location

 

Example #1 -

    (setq P1 (getpoint "\nInput Point ? "))    ;type at command prompt

    Input #1 -

        Command: Input Point ? pick point         ;Point Input

        returns: coordinates of picked point in list format

    Input #2 -

        Command: Input Point ? 25.0,25.0          ;Numeric Input

        returns: (25.0 25.0 0.0)

    Input #3 -

        Command: Input Point ? 25,25                 ;Numeric Input

        returns: (25.0 25.0 0.0)

    Input #4 -

        Command: Input Point ? S                        ;string input

        Invalid Point

        Input Point ?                                                ;allows user to re-input number

 

Example #2 -

    (setq P0 (list 0.0 0.0))

    (setq P1 (getpoint P0 "\nInput Point ? "))    ;type at command prompt

    Input #1 -

        Command: Input Point ? pick point             ;Point Input showing rubberband from P0

        returns: coordinates of picked point in list format

 

Note - getpoint will accept a single integer or real number as the pt argument, and use the AutoCAD direct distance entry mechanism to determine a point. This mechanism uses the value of the LASTPOINT system variable as the starting point, the pt input as the distance, and the current cursor location as the direction from LASTPOINT. The result is a point that is the specified number of units away from LASTPOINT in the direction of the current cursor location. This may produce unexpected results.