将文件nroff_file中的格式按下面的书写：
.TL
title of document
.AU
author name
.SH
section heading
.PP
paragraph ..
.PP
another paragraph ..
.SH
another section heading
.PP
etc.
用nroff来察看：
# nroff -ms nroff_file | more
效果：
title of document
author name
section heading
paragraph ..
another paragraph ..
another section heading
etc.
