Assuming that you are using the Startup Suite as part of the APPLOAD command dialog to automatically load your 'Startup' LISP program (which then subsequently loads other program files), I would instead suggest using the acaddoc.lsp file to automatically load your programs, as this is a far more reliable loading method.
To load programs using the acaddoc.lsp, perform the following procedure:
Check whether or not an acaddoc.lsp already exists. To do this, open AutoCAD to a new blank drawing, and type at the AutoCAD command-line:
(findfile "acaddoc.lsp")
If this returns a valid filepath, in the steps that follow, navigate to the filepath and open & modify the existing acaddoc.lsp using Windows Notepad or other plain text editor.
If the above expression returns nil, open Windows Notepad (or other plain text/code editor), and create a new acaddoc.lsp in a Trusted AutoCAD Support File Search Path.
On a new line in the acaddoc.lsp, enter the desired load or autoload expressions to load your custom programs, e.g.:
(load "MyProgram.lsp" "MyProgram.lsp failed to load.")
(autoload "MyProgram.lsp" '("MyCommand"))
Save the new/modified file and open a new drawing in AutoCAD to automatically load it.
Some Background on the acaddoc.lsp File
To provide a little background information on the nature and behaviour of the acaddoc.lsp file in AutoCAD: when opening a drawing, AutoCAD will search the Working Directory (that is, the directory in which the active drawing resides), and all Support File Search Paths (those listed in the Files tab of the Options dialog) for a file with the filename acaddoc.lsp.
In more recent AutoCAD releases in which the SECURELOAD system variable is present, only paths which are also listed as Trusted Paths will be considered by this search1.
When such a file is found, AutoCAD will cease searching and will proceed to load the acaddoc.lsp file into the active drawing namespace.
The act of loading a LISP file simply means that the contents of the file are read and any LISP expressions found therein are evaluated by the LISP interpreter.
In this way, most users will utilise the acaddoc.lsp to automatically load custom programs when a drawing is opened, so that such programs are available during the drawing session. This is a more reliable and migratable method than using the Startup Suite for the same purpose.
Similar Autoloading Files
Aside, note that the acaddoc.lsp is not the only file that is automatically sought and loaded into the active drawing...
When the AutoCAD application is initially opened, a number of files are automatically loaded and others are reloaded again when every drawing is opened thereafter.
Most of these files are part of the application itself and hence should not be modified, others however are reserved for user customisation and can be modified and created if they don't already exist.
Below is the loading order of the various files that are automatically loaded into AutoCAD, with a brief description about each item:
acad.rx
This file loads various ObjectARX applications when AutoCAD is started.
acad20##.lsp
This file loads the acad20##doc.lsp file in versions which do not load such file automatically. This file should not be modified.
acad.lsp
The loading of this file is dependent on the setting of the
ACADLSPASDOC system variable:
ACADLSPASDOC = 0 (default) Loads acad.lsp into just the first drawing opened in an AutoCAD session, and will not load for each subsequently opened drawing.
ACADLSPASDOC = 1 Loads acad.lsp into every drawing opened.
This file is reserved for user customisation and is intended to be used for application-specific startup routines, as all functions and variables defined in an
acad.lsp file are only available in the first drawing.
If functions are required in all drawings, rather than altering the value of
ACADLSPASDOC, functions & programs should be moved from the acad.lsp file into the acaddoc.lsp file.
acad20##doc.lsp
This file is automatically loaded every time a drawing is opened and loads the autoload function definiton and other utility functions required by AutoCAD. This file should not be modified.
acaddoc.lsp
As described above, if found, this file is automatically loaded into every drawing opened in the AutoCAD session. This file is useful for loading a library of AutoLISP functions to be available every time a drawing is opened.
The acaddoc.lsp file is always loaded with each drawing regardless of the settings of the ACADLSPASDOC system variable.
Since AutoCAD will search the working directory before the Support File Search Paths and will load the first acaddoc.lsp file found, users can have a different acaddoc.lsp file in each drawing directory, which would load specific AutoLISP routines for certain types of drawings or jobs.2
acad.dvb
This file will automatically load VBA projects for versions in which VBA is enabled.
Main CUI/CUIX and related files
A CUIx file contains multiple XML based files and image files, each of which contains the data for a user interface element that can be customised. CUIx files replace the CUI, MNU, MNS, and MNC files that were used to define menus in previouse releases.
The Main CUIx file defines the majority of interface elements in AutoCAD.
Enterprise CUI/CUIX and related files
The Enterprise CUIx file is typically controlled by a CAD manager and accessed by many users, usually from a shared network location.
This file is read-only to users to prevent the data in the file from being changed. A CAD manager would create an enterprise CUIx file by modifying a Main CUIx file and then saving the file to a shared network location.
acetmain.mnl
This file loads the Express Tools menugroups.
Express Tools LISP & MNL files
The various LISP and Menu files required by the Express Tools programs are loaded here.
Startup Suite programs
Programs files residing in the Startup Suite are now loaded, in the order they appear in the APPLOAD dialog.
As noted above, the Startup Suite is known to be temperamental in some versions of AutoCAD, so I would recommend using the acaddoc.lsp for loading functions and programs required during the drawing session.
(S::STARTUP)
This post-initialisation function can be utilised to perform operations after the drawing has initialised in the drawing editor.
Since the acad.lsp and acaddoc.lsp files are loaded early in the drawing initialisation procedure, commands issued at run-time from these files may be unsuccessful as the command-line may not be initialised in the drawing.
acad.exe command-line switch /b
The command-line switch /b can be used to run a Script when the AutoCAD application is launched. Any Script operations called in this way will be executed after drawing initialisation has completed.
Command-line switches can be set from within the properties of the AutoCAD application shortcut icon, within the Target edit box.
Footnotes
1 This was introduced to mitigate against AutoCAD 'viruses' in which a drawing file would be sent to a third-party along with an accompanying malicious acaddoc.lsp file residing in the same folder, such that when the drawing file was opened, AutoCAD would automatically evaluate the malicious acaddoc.lsp file.
2 This is only possible if the SECURELOAD system variable is set to 0.
