将手册页转储到文本通常会保留某些格式，例如 foo^H^H^H___ fo,包括下划线和其他特殊字符,col -bx删除了这些.
$ man2txt 1 cat | head
CAT(1) User Commands CAT(1)
NAME
cat - concatenate files and print on the standard output
SYNOPSIS
cat [OPTION]... [FILE]...
DESCRIPTION
Concatenate FILE(s) to standard output.