Thanks to Kean Walmsley’s post on his Through the Interface blog, I have learned something that would have been handy to know for the last decade or so, but which somehow escaped my knowledge. I learned how to increase the size of AutoCAD’s command line history cache. It defaults to 400 lines, which isn’t enough for me. I think this information deserves a wider audience than the ubergeek developers who frequent Kean’s blog, so here goes.

Although it’s not directly mentioned on Kean’s post, you can find the current command line history cache length setting like this:

(getenv "CmdHistLines")

This will return a value showing the number of command lines AutoCAD remembers, e.g. “400”. Although this is used as an integer value, it is passed to and from the Registry as a string. You can set a new value as shown below. Again, use a string, and note that values outside the range 25 to 2048 will be ignored:

(setenv "CmdHistLines" "2048")

Also, if you don’t like AutoCAD repeatedly stopping during a long listing (e.g. SETVAR ? *), you can turn off that feature by setting the QAFLAGS system variable to 2. Don’t set it to 8191 as suggested in Kean’s post, because that will change a lot of other settings, few of which are documented publicly.