好久没碰数学，很多数学符号发音都忘了，读一些文章时特别别扭，所以从网上搜了一下，运气还不错，已经有网站收集了数学符号及其发音，参考这里和这里。

 

序号	大写	小写	英文注音	国际音标注	中文注音	意义
1	Α	α	alpha	a:lf	阿尔法	角度；系数
2	Β	β	beta	bet	贝塔	磁通系数；角度；系数
3	Γ	γ	gamma	ga:m	伽马	电导系数（小写）
4	Δ	δ	delta	delt	德尔塔	变动；密度；屈光度
5	Ε	ε	epsilon	ep`silon	伊普西龙	对数之基数
6	Ζ	ζ	zeta	zat	截塔	系数；方位角；阻抗；相对粘度；子序数
7	Η	η	eta	eit	艾塔	磁滞系数；效率（小写）
8	Θ	θ	thet	θit	西塔	温度；相位角
9	Ι	ι	iot	aiot	约塔	微小，一点儿
10	Κ	κ	kappa	kap	卡帕	介质常数
11	Λ	λ	lambda	lambd	兰布达	波长（小写）；体积
12	Μ	μ	mu	mju	缪	磁导系数；微（千分之一）；放大因数（小写）
13	Ν	ν	nu	nju	纽	磁阻系数
14	Ξ	ξ	xi	ksi	克西
15	Ο	ο	omicron	omik`ron	奥密克戎
16	Π	π	pi	pai	派	圆周率=圆周÷直径=3.1416
17	Ρ	ρ	rho	rou	肉	电阻系数（小写）
18	Σ	σ	sigma	`sigma	西格马	总和（大写），表面密度；跨导（小写）
19	Τ	τ	tau	tau	套	时间常数
20	Υ	υ	upsilon	jup`silon	宇普西龙	位移
21	Φ	φ	phi	fai	佛爱	磁通；角
22	Χ	χ	chi	phai	西
23	Ψ	ψ	psi	psai	普西	角速；介质电通量（静电力线）；角
24	Ω	ω	omega	o`miga	欧米伽	欧姆（大写）；角速（小写）；

 

1  Α  α  alpha  a:lf        阿尔法  角度；系数 
2  Β  β  beta  bet          贝塔  磁通系数；角度；系数 
3  Γ  γ  gamma  ga:m      伽马  电导系数（小写） 
4  Δ  δ  delta  delt      德尔塔  变动；密度；屈光度 
5  Ε  ε  epsilon  ep`silon  伊普西龙  对数之基数 
6  Ζ  ζ  zeta  zat          截塔  系数；方位角；阻抗；相对粘度；原子序数 
7  Η  η  eta  eit           艾塔  磁滞系数；效率（小写） 
8  Θ  θ  thet  θit           西塔  温度；相位角 
9  Ι  ι  iot  aiot            约塔  微小，一点儿 
10  Κ  κ  kappa  kap       卡帕  介质常数 
11  ∧  λ  lambda  lambd  兰布达  波长（小写）；体积 
12  Μ  μ  mu  mju          缪  磁导系数；微（千分之一）；放大因数（小写） 
13  Ν  ν  nu  nju          纽  磁阻系数 
14  Ξ  ξ  xi  ksi          克西  　 
15  Ο  ο  omicron  omik`ron  奥密克戎  　 
16  ∏  π  pi  pai          派  圆周率=圆周÷直径=3.14159 26535 89793 
17  Ρ  ρ  rho  rou          肉  电阻系数（小写） 
18  ∑  σ  sigma  `sigma  西格马  总和（大写），表面密度；跨导（小写） 
19  Τ  τ  tau  tau          套  时间常数 
20  Υ  υ  upsilon  jup`silon  宇普西龙  位移 
21  Φ  φ  phi  fai          佛爱  磁通；角 
22  Χ  χ  chi  phai          西    
23  Ψ  ψ  psi  psai      普西  角速；介质电通量（静电力线）；角 
24  Ω  ω  omega  o`miga  欧米伽  欧姆（大写）；角速（小写）；角

1. use mkfile(1M) to add swap file

• mkfile -v 64m swapfile
• swap -a /path/to/swapfile
• swap -lh
• swap -d /path/to/swapfile 

2. use mkfile(1M) to learn zfs

• mkfile 64m /tmp/a /tmp/b /tmp/c
• zpool create mypool mirror /tmp/a /tmp/b
• zpool status 

3. use mkfile(1M) to create a UFS inside one file

•  Create file: # mkfile 200m /export/home/test
• Attach file to a block device: # lofiadm -a /export/home/test then /dev/lofi/1 will be created
• Create a UFS file system: # newfs /dev/rlofi/1
• Mount device: # mount /dev/lofi/1 /mnt
• Display the space: # df -h /mnt
• Unmount: # umount /mnt
• Delete block device: # lofiadm -d /dev/lofi/1
  

1. Books on C programming languages

The C Programming Language, Kernighan and Ritchie, 2nd Edition. Still reads well. I still have and use the first edition dated 1978. See <http://cm.bell-labs.com/cm/cs/cbook/>.

C Puzzle Book, Alan R Feuer, Addison-Wesley, 2nd edition 1999, ISBN 0201604612. The best ever book on understanding the quirks of C and how to use pointers properly.

The Practice of Programming, Kernighan and Pike, Addison-Wesley, 1999. An update of an earlier book written in the 1970s. Timeless advice, not just on C but on Java, C++ and Perl. See <http://cm.bell-labs.com/cm/cs/tpop/>.

The Standard C Library, PJ Plauger, Prentice Hall, 1992. Literally how it all works with full source code and tests.

2. Some intresting articles and books

Interview with Brian Kernighan	Enjoyable reading with some support for our views on C++. Plus advice on how to pronounce his name correctly.
comp.lang.c Frequently Asked Questions	Link to www version. Highly relevant. An up-to-date copy may be obtained from ftp.eskimo.com in directory u/s/scs/C-faq/. 中文faq的地址（提供了PDF格式）：http://c-faq-chn.sourceforge.net/ccfaq/node1.html
ANSI C Programming Lanuage	A useful short help on C Programming, including precedence and the preprocessor.
ANSI C Standard Library	Summary of the ANSI C standard library functions (that's the real ANSI C).
Rationale for ANSI C	A link to the original Rationale for American National Standard for Information Systems - Programming Language - C. This was included in the original ANSI standard explaining why things were done as they were. It was unfortunately dropped from the ISO standard.
Style in C	Rob Pike's set of essays on coding style and a "philosophy of clarity in programming" as opposed to laying down hard rules.
C Traps and pitfalls	An essay by Andrew Koenig of AT&T Bell Labs written as the basis to his book C Traps and Pitfalls. "The C language is like a carving knife: ... This paper shows some of the ways C can injure the unwary, and how to avoid injury." Worth reading (and then re-reading).
How To Steal Code	Henry Spencer's article on inventing the wheel only once. "Never build what you can (legally) steal! Done right, it yields better programs for less work". There are some useful C programs at the end.
The Ten Commandments for C Programmers	Henry Spencer's amusing, but true, adaptation of the ten commandments for C programmers. We love number 6: If a function be advertised to return an error code in the event of difficulties, thou shalt check for that code, yea, even though the checks triple the size of thy code and produce aches in thy typing fingers, for if thou thinkest ``it cannot happen to me'', the gods shall surely punish thee for thy arrogance. Read and take note.
How to write unmaintainable code     Expert C Programming	A link to Roedy Green's very amusing article on how to guarantee a lifetime's employment by making life impossible for maintenance programmers. (He actually has to explain that it's a joke!) Although focused on Java, he gives plenty of examples in C. If you give someone a program, you will frustrate them for a day; if you teach them how to program, you will frustrate them for a lifetime. More quotes below.   很不错的一本书，不过包含很多看似和语言无关的东西，我第一遍看的时候都跳过去了。这也造成本书的组织有点散。

 

 

References

• http://www.di-mgt.com.au/cprog.html
• c程序设计之四书五经：http://www.channel7.cn/2004/9-30/21616.html
• 更多书籍：http://freecomputerbooks.com/
• 195 Free Online Programming Books： http://www.techtoolblog.com/archives/195-free-online-programming-books

 

确定数组的长度

通常我们需要在一个循环中遍历数组的所有元素，因此需要知道数组的长度。硬编码数组长度显然是不可取的，因为如果改变数组元素的个数的话，需要改动多处代码。使用下面的方式可以很好的避免这个问题：

char * hero[][2] = {
       { "Guo Jing", "She Diao" },
       { "Ling Huchong", "Xiao ao Jiang Hu" },
       { "Yang Guo", "Shen Diao" },
       { "Hu Fei", "Xue Shan Fei Hu" },
    };

for (i=0; i < sizeof (hero) / sizeof (*hero); i++)
{
    printf ("%s come from %s\n", hero[i][0], hero[i][1]);
}

[转载]NULL 0 \0以及nul的区别

信息来源：cprogramming.com

NULL is a macro defined in several standard headers, 0 is an integer constant, '\0' is a character constant, and nul is the name of the character constant. All of these are *not* interchangeable:

NULL is to be used for pointers only since it may be defined as ((void *)0), this would cause problems with anything but pointers.

Use cc -E you can see what NULL means on solaris. Commonly NULL is defined by "#define NULL 0" or "#define NULL (void *)0"

0 can be used anywhere, it is the generic symbol for each type's zero value and the compiler will sort things out.

'\0' should be used only in a character context.

nul is not defined in C or C++, it shouldn't be used unless you define it yourself in a suitable manner, like:

#define nul '\0'

empty string "" is "\0"

 

匿名参数的使用

有时候我们需要使用匿名参数以匹配指定的接口，譬如g_list_foreach()函数需要他的函数参数有两个参数，而如果我们把g_free传递给他时会报告错误，这样我们就可以使用一个函数封装g_free。例如

o_free (gpoint p, gpoint /* data */)

如何写可变参数函数

void va_start(va_list pvar, name): 根据name参数获得可变参数的指针 pvar。
(type *) va_arg(va_list pvar, type): 获得下一个可变参数，需要指定参数的类型。
void va_end(va_list pvar): 结束使用可变参数，使它不再指向内存有效地址。

例如：
void simple_va_func (int i, ...)
{
    va_list arg_ptr;
    int j = 0;

    va_start (arg_ptr, i);
    //这里的arg_ptr可以传递给任意函数作为参数，在那个函数内需要使用va_* 宏去获得对应的参数。
    j = va_arg (arg_ptr, int); 
    va_end (arg_ptr);

    return;
}

如何实现可变参数

可变参数的实现与具体的编译器/硬件平台相关，我们这里简单看一下 cdecl calling convention 下的参数传递。

cdecl模式下参数从右向左压入堆栈，而且是由调用者来做这个操作。
                          
                                               内存高地址（x86平台）
+-----------------------------+
| 最后一个可变参数     |
+-----------------------------+
| 倒数第二个可变参数 |
+-----------------------------+
|          ......                      |
+-----------------------------+
| 第一个可变参数         |      va_start 之后，arg_ptr 指向这里
+-----------------------------+
| 最后一个固定参数     |      这个参数的名字需要传递给va_start
+-----------------------------+
|          ......                      |
+-----------------------------+
| 第一个参数                 |
+-----------------------------+
| 函数返回地址             |
+-----------------------------+
| 调用者的 BP               |     被调用函数的栈基址
+-----------------------------+
| 局部变量                     |
+-----------------------------+

注意事项

• 实际调用时，被调用函数不知道实际传来的参数的个数，因此需要在程序内使用某种方式来判断是否是最后一个参数，例如NULL， -1 ，或者使用固定参数来说明参数的个数类似于main函数，等等
• 不能没有固定参数只有可变参数，例如 int f (...) { }
• va_arg()参数类型的使用需要注意： char, short 会被扩展成 int， float会被扩展成double。
• 使用函数作为一个可变参数时需要特别注意，参见reference2
  

参考

C语言中可变参数的用法
水滴石穿C语言之可变参数问题
CSDN C/C++电子杂志第一期 之 可变参数学习笔记