SEQCHK-bgol (Check Missing & Duplicate Numbers in Sequence)

Command Type: AutoLISP routine (works in AutoCAD, BricsCAD, ZWCAD and most AutoLISP-compatible CAD platforms)
Developed by: BGol Community, bgol.in

Inspired by the general concept of missing/duplicate sequence-number checking utilities used in survey/CAD drafting. This is an original, independently written routine, new file name, new command name, new source code, created so the CAD community has a free, editable, open-source alternative.

Overview

SNCK scans a selection of numeric TEXT entities (parcel numbers, point numbers, etc.), determines the minimum and maximum value present, and reports every missing number and every duplicated number within that range, a fast QA/QC pass on any serially-numbered drawing.

How to Use

1. Load SEQCHK-bgol.lsp into your CAD session (drag-and-drop the file onto the drawing window, or use the APPLOAD command).
2. Type SNCK at the command line and press Enter.
3. Select the numeric TEXT entities to check (e.g. all point number labels in an area), then press Enter to confirm.
4. The command line reports the checked range, the count and full list of missing numbers, and the count and full list of duplicated numbers. Every duplicated text entity is also marked with a point on layer BGOL-SNCK (colour red) so it can be located visually.
5. Press F2 to open the CAD text window if the command-line output is truncated.

Why Use It

• Error Detection at Scale, makes it feasible to check numbering integrity across large, complex drawings where manual review would be impractical.
• Time Savings, instantly reports both missing and duplicate numbers in one command instead of manual sorting/counting.
• Direct, Actionable Output, results are listed explicitly, and duplicates are marked in the drawing, so the exact items needing correction are known immediately.

Where to Use It

• Parcel numbering, verifying every land parcel in a subdivision or survey plan has a unique, sequential number with no gaps or duplicates.
• Any serial numbering system (point numbers, structure IDs, chainage markers) that must be checked for completeness and uniqueness before finalizing a drawing.
• General QA/QC pass on any drawing using sequential numeric labeling.

Notes

• The checked range always runs from the minimum to the maximum value found in the selection, numbers outside that range are not reported.
• Non-numeric text in the selection is treated as 0; keep the selection limited to genuinely numeric labels for reliable results.
• Source code is fully open, feel free to study, modify, and redistribute it under the same open, free-for-all spirit.

Credits

Developed and shared for the CAD community by BGol Community. Website: https://bgol.in/ Free and open-source, use it, modify it, share it, for personal or commercial work alike.