Linux的man那點事

用過linux的朋友估計沒有誰不熟悉man命令，大家都知道利用它可以查看到linux絕大部分命令的使用方法（但不是全部），除了這個你還了解它什麼呢？其實了解man可以查看其它命令的使用方法就掌握了它的核心，但是最近看書的時候又找到了它的一點其他信息。哈哈，你就將這篇文章當做扯談吧！~

1. man其實是manual的縮寫(不會很多人認為它是"男人"吧)，表示手冊、指南的意思。

2. 其實man也包含8個部分。

man1: User programs
Manual pages that describe publicly accessible commands are contained 
in this chapter. Most program documentation that a user will need to 
use is located here.

man2: System calls
This section describes all of the system calls (requests for the kernel 
to perform operations).

man3: Library functions and subroutines 
Section 3 describes program library routines that are not direct calls 
to kernel services. This and chapter 2 are only really of interest to
programmers.

man4: Special files
Section 4 describes the special files, related driver functions, and 
networking support available in the system. Typically, this includes 
the device files found in /dev and the kernel interface to networking 
protocol support.

man5: File formats
The formats for many data files are documented in the section 5. This 
includes various include files, program output files, and system files.

man6: Games
This chapter documents games, demos, and generally trivial programs.
Different people have various notions about how essential this is.

man7: Miscellaneous Manual pages that are difficult to classify are 
designated as being section 7. The troff and other text processing 
macro packages are found here.

man8: System administration Programs used by system administrators
for system operation and maintenance are documented here. Some of
these programs are also occasionally useful for normal users.

我們平常主要用到的是man1和man5，當我們敲出man命令時，www.linuxidc.com默認的就是man1，例如man ls實際上等價的就是man 1 ls。這是最常用的，此時man會告訴我們這個命令(程序)的用法。而平常也偶爾會用到man5，比如你要查看/etc/fstab這個文件裡面每一行每一列的的解釋那麼你就可以使用 man 5 fstab。那麼你就可以得到相關解釋信息。至於其他的man，估計很少會用到。

這些man的所對應的信息都是在/usr/share/man/這個目錄下：

xxx@db-2:~$ ls /usr/share/man
cs de es fi fr gl hu id it ja ko man1 man2 man3 man4 man5 man6 man7 man8 nl pl pt pt_BR ru sv tr zh_CN zh_TW

其實每個manx的目錄下的每個文件都是程序名或者稱為命令名+x+.gz組成的，你解壓之後可以看到裡面是文本信息。另外，我們在man查看命令使用方法時，經常會看到第一行有command(數字),還有最後的SEE ALSO部分也是command(數字)這種信息，其實括號裡面的信息就是表面你可以通過man 數字 command可以查看到相關信息，比如 man mkfs。

好了。