TableOfContents

1. 关于我

个人信息

2. C

2.1. Coding Style

• 先看 [http://lxr.linux.no/source/Documentation/CodingStyle Linux kernel coding style]

2.1.1. Indentation

• 8-char indent
• If you need more than 3 levels of indentation, you're screwed anyway, and should fix your program.
• Don't put multiple statements on a single line unless you have something to hide.
• Get a decent editor, and don't leave whitespace at the end of lines.

2.1.2. Breaking long lines and strings

• Coding style is all about readability and maintainabilty using commonly avaible tools.
• The limit on the length of lines is 80 colums and this is a hard limit.

2.1.3. Placing braces

• The preferred way, as shown to us by the prophets Kernighan and Ritchie, is to put the opening brace last on the line, and put the closing brace first.
• namely function have the opening brace at the begining of the next line.

2.1.4. Naming

• C is a Spartan language, and so should your naming be.
• GLOBAL variables (to be used only if you _really_need them) need to have descriptive name, as do global functions.
• LOCAL variable name should be short, and to the point.

2.1.5. Fuctions

• Fuctions should be short and sweet, and do just one thind.
• Another measure of the functions is the number of local variables, They shouldn't exceed 5-10, or you're doing something wrong.

2.1.6. Centralized exiting of functions

• About gogo statement.

2.1.7. Commenting

• Comments are good, but there is also a demage of over-commenting.
• Generally, you want your comments to tell WHAT your code does, not HOW.

2.1.8. You've made a mess of it

• About GNU Emacs and GNU indent.
• 'indent' is not a fix for bad programing.

2.1.9. Data structures

• Data structures that have visibility outside the single-threaded environment they are created and destoryed in should always have reference counts.
• Locking is _not_ a replacement for reference counting.
• If another thread can find your data structure, and you don't have a reference count on it, you almost certainly have a bug.

2.1.10. Macros, Enums, Inline functions and RTL

• Names of macros defining contants and labels in enums are capitalized.
• Enums are preferred when defining serval related constants.
• Generally, inline functions are preferable to macros resembling functions.
• Macros with multiple statements should be enclosed in a do-while block.

2.2. malloc, calloc, free

• 一个严重的错误：释放不是通过调用 malloc, calloc 得到的指针所指向的存储空间。
• 使用已释放空间同样是错误的。

3. GNU Tools

3.1. Vim

• 先看 [http://chinaunix.net/jh/28/194152.html 进行有效编辑的七种习惯] by Bram Moolenaar, the author of vim.

• 再看 [http://www-128.ibm.com/developerworks/cn/linux/l-tip-vim1/ Vim 实用技术] at DeveloperWorks.

3.1.1. Edit a file

3.1.1.1. Move around quickly

• If you set the incsearch option, Vim will show the first match for the pattern, while you are still typing it. This quickly shows a typo in the pattern.

• If you set hlsearch option, Vim will highlight all matches for the pattern with a yellow background. :nohlsearch will close it.

• If you see a specific word and want to search for other occurrences of the same word, use the * command to grab the word from under the cursor and search for the next one, while # search for the previous one.

• In structured text(C/C++)

  • % can jump to many different matching items. It is very useful to check if() and {} constructs are balanced properly.

  • Use [{ to jump back to the "{" at the start of the current code block, and ]} for '}'.

  • Use gd to jump from the use of variable to its local declaration.

• 可视（visual）模式，用于选定文本块；可以在正常模式下输入v（小写）来按字符选定，输入V（大写）来按行选定，或输入Ctrl-V来按方块选定。

• `.（跳转到最近修改过的位置）

• ZQ（无条件退出）

• ZZ（存盘退出）

• ga（显示光标下的字符在当前使用的 encoding 下的内码）

• guw（光标下的单词变为小写）

• gUw（光标下的单词变为大写）

• :TOhtml （根据 Vim 的语法加亮的方式生成 HTML 代码）

• K （显示光标下单词的 man 手册页）

• 将当前行提到页首：zt，页尾：zb。

• gg 定位到文件开头，G 定位到文件的结尾。

3.1.1.2. Don't type it twice

• If you want to change one word into another in the whole file, you can use the :s(substitute) command.

  • 去掉所有的行尾空格：“:%s/\s\+$//”。

  • 去掉所有的空白行：“:%s/\(\s*\n\)\+/\r/”。

  • 去掉所有的“//”注释：“:%s!\s*//.*!!”。

  • 去掉所有的“/* */”注释：“:%s!\s*/\*\_.\{-}\*/\s*! !g”。

• If you want to change one word into another only a few locations, a quick method is to use the * command to find the next occurrence of the word and use cw to change the word. Then type n to find the next word and .(dot) to repeat the cw command.

• CTRL-N can auto complete function and variable names. Vim looks up words in the file you are editing, and also in #include'd files.

• Vim has a mechanism to record a macro. You type qa to start recording into register 'a'. Then you type your commands as usual and finally hit q again to stop recording. When you want to repeat the recorded commands you type @a.

• 寄存器
  • 除了有一个无名寄存器外，Vim 还有一大堆有名的寄存器，可以通过“"”（参见“:help "”）或“Ctrl-R”（参见“:help i_CTRL-R”和“:help c_CTRL-R”）加寄存器名（字母、数字和某些特殊字符，参见“:help registers”；“无名”寄存器的名字是“"”）来访问。比如，你先使用“"ayy”复制了一行，然后使用“dd”删掉了一行，然后移动光标到要复制到的位置，就可以使用“"aP”把先前复制的内容粘贴上去了。
  • 在使用 X Window 系统时，有两个特殊的寄存器是需要注意一下的：“"*”访问的寄存器是 X 的主选择区域（primary selection），“"+”访问的寄存器是 X 的剪贴板（clipboard）。
  • 还有一个很特殊的“寄存器”：“=”。在插入模式或命令模式中，键入“Ctrl-R=”，Vim 会提示你输入一个表达式，普通的整数运算在此完全有效。

3.1.1.3. Fix it when it's wrong

• It's normal to make errors while typing, this can be corrected with abbreviations: :abbr Lunix Linux.

• The same mechanism can be used to type a long word with just a few characters: :abbr pn pinguin.

• To find errors in your text Vim has a clever hightlighting mechanism. This was actually meant to be used to do syntax hightlighting of programs, but it can catch and highlight errors as well.

• Modeline for C coding style(see above): /* vim:shiftwidth=8:tabstop=8:filetype=c:norl: */

  • 把光标移到要重新格式化的文本开头，使用gq命令后面跟一个光标移动命令确定重新格式化的范围。比如gq}（格式化一段），gq5j（格式化 5 行），gqG（格式化至文件末尾）。

• :set list 查看所有不可见字符; :set nolist 关闭

• A more complex example: English text.

3.1.2. Edit more files

3.1.2.1. A file seldom comes alone

• Tag mechanism works for jumping between files.
  • :tag 关键字（跳转到与“关键字”匹配的标记处）
  • :tselect [关键字]（显示与“关键字”匹配的标记列表，输入数字跳转到指定的标记）
  • :tjump [关键字]（类似于“:tselect”，但当匹配项只有一个时直接跳转至标记处而不再显示列表）
  • :tn（跳转到下一个匹配的标记处）
  • :tp（跳转到上一个匹配的标记处）
  • Ctrl-]（跳转到与光标下的关键字匹配的标记处；除“关键字”直接从光标位置自动获得外，功能与“:tags”相同）
  • g]（与“Ctrl-]”功能类似，但使用的命令是“:tselect”）
  • g Ctrl-]（与“Ctrl-]”功能类似，但使用的命令是“:tjump”）
  • Ctrl-T（跳转回上次使用以上命令跳转前的位置）

• Another powerful mechanism is to find all occurrences of a name in a group of files, using the :grep command. Vim makes a list of all matches, and jumps to the first one. The :cn command takes you to each next match.

• Positions the cursor on the name of the function in your file and type [i: Vim will show a list of all matches for the function name in the included files.

• In vim you can split the text erea in several parts to edit different files.

  • :split 上下分屏； :vsplit 左右分屏。

• There are more uses of multiple window. The preview-tag mechanism is a very good example.
• 可以使用“gf”命令方便地跳转到光标下的文件名所代表的文件中。使用“Ctrl-O”（参见“:help CTRL-O”）可返回到原先的文件中。

3.1.2.2. Let's work together

• Select some structured text in a list and sort it: !sort.

• 如果想把外部命令执行的结果插入到当前编辑的缓冲区中，可以考虑使用“:r!”。

• 当使用可视模式选中文本行后然后键入“:!”（命令行上将出现“:'<,'>!”，表示命令的范围是选定的文本），或者使用“:%!”（表示命令的范围是整个缓冲区中的文本），Vim 在执行后面的命令时，将把命令范围里的文本行作为后面执行的命令标准输入，并用命令执行后的标准输出替换当前缓冲区中的这些文本行。

  • 要对所有的非空行进行编号，只需要“:%!nl”；要对包含空行的所有行进行编号？OK，“:%!nl -ba”。

3.1.2.3. Text is structured

• One of the simpler things is to speed up the edit-compile-fix cycle. Vim has the :make command, which starts your compilations, catches the errors it produces and lets you jump to the error locations to fix the problems.

  • :cn（显示下一个错误）
  • :cp（显示上一个错误）
  • :cl（列出所有的错误及其编号）
  • :cc（跳转到指定编号的错误）
  • :copen（打开快速修订窗口，在其中显示所有错误，可在错误上双击鼠标或按回车键跳转至该错误）

3.1.3. Sharpen the saw

3.1.3.1. Make it a habit

• You need to learn new commands and turn them into a habit.

3.1.4. Task

3.1.4.1. Editing in hex mode

1. vim -b NSLU2?_v23R29.bin
2. :%!xxd
3. When completed, :%!xxd -r

3.2. CVS

• 先看 [http://www.chedong.com/tech/cvs_card.html CVS使用手册] by Chedong.

4. File System

• 先看 [http://www.debian-administration.org/articles/388 Filesystems (ext3, reiser, xfs, jfs) comparison on Debian Etch].

4.1. Ext3

• 稳定，中庸

4.2. JFS

• JFS is the lowest CPU-usage FS.

4.3. ReiserFS

• It's the only filesystem that supports shrinking a filesystem now
• Nothing here will shake my own choice of ReiserFS for most general purpose filesystems, it has a good performance on real world benchmarks, and is the most mature of the journalling file systems presented.(simonw)

4.4. XFS

• http://en.wikipedia.org/wiki/XFS

• [http://www.madpenguin.org/cms/html/67/6045.html File System Design part 1: XFS]

Technical Specifications:

• Journaled 64-bit filesystem with guaranteed filesystem consistency.
• Online Administration: XFS supports filesystem growth for mounted volumes, allows filesystem "freeze" and "thaw" operations to support volume level snapshots, and provides an online file defragmentation utility.
• Quotas: XFS supports user and group quotas. XFS considers quota information as filesystem metadata and uses journaling to avoid the need for lengthy quota consistency checks after a crash.
• XFS supports the ACL semantics and interfaces described in the draft POSIX 1003.1e standard.

XFS appears to be the most appropriate filesystem to install on a file server for home or small-business needs :

• It uses the maximum capacity of your server hard disk(s)
• It's the quickest FS to create, mount and unmount

• It's the quickest FS for operations on large files (>500MB)

• This FS gets a good place for operations on a large number of small to moderate-size files and directories
• It constitutes a good CPU vs time compromise for large directory listing or file search

5. Samba

5.1. CIFS 修改之主要目的

• 简化与精练 SMB 协议中一些比较混乱的部分
• 增加 unicode 支持
• 改善文件锁
• 支持硬连接
• 彻底消除对 NetBIOS 的依赖
• Linux 增强 SMB-Unix 非 Windows 的文件类型（如：符号连接）

6. 反馈

欢迎大家对我说三道四哪