The m3 command recognizes files with these extensions.
Arguments that name directories are searched recursively. Any files with recognized suffixes (.i3, .m3, .ic, .mc, .c, .is, .ms, .s, .io, .mo .o, .a) found in those directories are effectively added to the command line. Any directories containing .i3 files are prepended to the -D search path.
m3-request@src.dec.com
Last modified on Mon Sep 25 18:31:52 PDT 1995 by heydon modified on Thu Apr 21 16:04:27 PDT 1994 by kalsow modified on Fri Feb 7 00:38:19 PST 1992 by muller