Linux的man那点事

用过linux的朋友估计没有谁不熟悉man命令，大家都知道利用它可以查看到linux绝大部分命令的使用方法（但不是全部），除了这个你还了解它什么呢？其实了解man可以查看其它命令的使用方法就掌握了它的核心，但是最近看书的时候又找到了它的一点其他信息。哈哈，你就将这篇文章当做扯谈吧！~

1. man其实是manual的缩写(不会很多人认为它是"男人"吧)，表示手册、指南的意思。

2. 其实man也包含8个部分。

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.

我们平常主要用到的是man1和man5，当我们敲出man命令时，默认的就是man1，例如man ls实际上等价的就是man 1 ls。这是最常用的，此时man会告诉我们这个命令(程序)的用法。而平常也偶尔会用到man5，比如你要查看/etc/fstab这个文件里面每一行每一列的的解释那么你就可以使用 man 5 fstab。那么你就可以得到相关解释信息。至于其他的man，估计很少会用到。

这些man的所对应的信息都是在/usr/share/man/这个目录下：

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

其实每个manx的目录下的每个文件都是程序名或者称为命令名+x+.gz组成的，你解压之后可以看到里面是文本信息。另外，我们在man查看命令使用方法时，经常会看到第一行有command(数字),还有最后的SEE ALSO部分也是command(数字)这种信息，其实括号里面的信息就是表面你可以通过man 数字 command可以查看到相关信息，比如 man mkfs。

好了，扯谈完毕~