Arguments

pathname  string, any file or folder name to search

Return

string, the fully qualified folder or file name, or NIL if no such file or folder is found

Example

(findfile "bricscad.exe")  "c:\\Program Files\\.....\\bricscad.exe"

Remarks

forward and backward slashes are automatically handled, according to the actual platform (Windows, Linux, Mac),
so both specifications "\\" and "/" work on all platforms;

the folder and file search uses the SupportPathes (SRCHPATH system variable);
relative folder and file names are supported :
(findfile "subDir/MyLispFile.lsp")