man ls
man execl
man是manuals的缩写，不仅可以查看可执行程序的manual，还可以查看其他的如函数的manual，具体描述可以通过命令man man查看
最简单的例子：
echo hello test > testcmd.1
gzip -c testcmd.1 > /usr/share/man/man1/testcmd.1.gz
man testcmd
这样就可以看到testcmd的man手册了。但是内容相当简陋，甚至都不需要有对testcmd的支持，不需要真的有这么一个程序，不需要有这么一个函数，不需要有这么一个库。
要想像linux标准命令一样友好，需要提升可阅读性。
简单小结：
man手册中的内容是groff标准方式编写，然后压缩为gz格式存放到指定目录
man存放路径：
命令manpath可以获得，可以ls /etc | grep man获取配置文件路径，centos获取到的是man_db.conf，如上以 /usr/share/man 路径为例。
要想man手册友好，就要用groff标准编写，先列举groff的标准宏
Macro Description
.B Bold
.BI Bold, then italics (alternate)
.BR Bold, then roman (alternating)
.DT Set default tabs
.HP Begin a hanging indent
.I Italics
.IB Italics, then bold (alternating)
.IP Begin hanging tag. For options. Long tags use .TP.
.IR Italics, then roman (alternating)
.LP Begin paragraph
.PD Set distance between paragraphs
.PP Begin paragraph
.RB Roman, then bold (alternating)
.RE End relative indent (after .RS)
.RI Roman, then italics (alternating)
.RS Begin relative indent (use .RE to end indent)
.SB Small text, then bold (alternating)
.SM Small text. Used to show words in all caps.
.SH Section head
.SS Subheading within a .SH heading.
.TH Title heading. Used once at the beginning of the man page.
.TP Begin a hanging tag. Begins text on next line, not same line as tag.编辑文件时，换行不是真的换行，只会多出一个空格，所以要用Macro换行.TP .PP
实例：
.TH test "three corner" "middle bottom" "left bottom" "middle top"
.SH section
.TP
this is a paragraph
.PP
this is a new paragraph
this is not a new line
.SH DESCRIPTION
. this line will not display
.TP
.B \.B
means a bold font
.TP
\fB\\fB...\\fR\fR
the content in [\\fB \\fR] will show font as bold too .
.TP
.B \.TH
title heading, append 5 param,
.RS
param 1 and 2 as a,b: a(b) will display at left top, right top, right bottom
.RE
.RS
param 3 as c: c will display at middle bottom
.RE
.RS
param 4 as d: d will diaplay at left bottom
.RE
.RS
param 5 as e: e will display at middle top
used once at the beginning of the man page
.RE
.TP
.B \.SH
section head such as the section DESCRIPTION,
.SS subheading
.TP
.B \.SS
subheading such as above
.TP
.B \.TP or \.PP
if the paragraph start with \.TP, and the tags' length >= 7, the next content will display at next line
.TP
.B \.TP
if the paragraph start with \.TP, and the tags' length < 7, the next content will append the tags
.PP
.B \.PP or \.TP
if the paragraph start with \.PP, even if the tags' length >= 7, the next content will append at the tags
.PP
this is a new linw with PP
.TP
.I \.I
means a italics font, \fB\-I\fR=\fIitalics\fR. \\fI...\\fR show as \fI...\fR
.TP
.SB \.SB
.SB means small text,then bold
.HP
.B \.HP
begin a hanging indent
.HP
a new lin with HP
把如上内容写入到testcmd.1文件中，再执行如下命令
gzip -c testcmd.1 > /usr/share/man/man1/testcmd.1.gz
man testcmd
便能看到稍微友好一些的输出了，实例中使用了部分Macro，但是也够用了
是不是稍微有模有样了。
小贴士：
修改centos终端标题：
export PS1="${PS1}\[\e]2;new title\a\]"
或者
PROMPT_COMMAND='echo -ne "\033]0;new title \007"'new title就是新的标题
