The GNU Troff Manual
5.22.1 Copy-in Mode
When gtroff reads in the text for a macro, string, or diversion,
it copies the text (including request lines, but excluding escapes) into
an internal buffer. Escapes are converted into an internal form,
except for \n, \$, \*, \\ and
\RET which are evaluated and inserted into the text where
the escape was located. This is known as copy-in mode or
copy mode.
What this means is that you can specify when these escapes are to be
evaluated (either at copy-in time or at the time of use) by insulating
the escapes with an extra backslash. Compare this to the \def
and \edef commands in TeX.
The following example prints the numbers 20 and 10:
| | .nr x 20
.de y
.nr x 10
\&\nx
\&\\nx
..
.y
|
