Scritping

awk命令是允许程序员依照模式来查找文件以及修改这些文件中的记录的编程语言。awk起名始源于它的三个创始者姓氏的第一个字母的合称。从1978年开始，awk已经成为UNIX系统的一部分。目前有三种版本的awk：原始的awk；新版的nawk；POSIX/GUN版本的gawk。

A project defiens one or more targets and any number of properties. One of the most powerful features of the ant framework is the ability to define properties inside and outside of the project file. The target is the key building block for ant. A target defiens a sequence or block of tasks that are to be executed. The target block is a very powerful piece of the ant frameworkbecause it is from the target that dependencies occur.

The if attribute will look for a given property and if it has been defined, the target will be triggered for execution.Conversely, if the property defined in unless is not found , the target will be triggered for execution.

The task is where all the real work is performed. This is the actual command that is executed inside the target. A task can take any number of attributes and can be any legally formatted xml tag.

A listener is a component that is alerted to certain events during the life of a build. A logger is built on top of a listener, and is the component that is responsible for logging information about the build.

At its most basic ,all a good build tool does is take source code, compile it and create a working applicatiom. Ant provides extensive support for controllling the build process; though ant is not a programming lanuage, it has a number of control structures, and those control structures rely on properties.  The foundation to any type of control processing is some form of the if statement.

可以利用xmlvalidate任务来验证XML文档是否符合DTD或者XML schema的定义。构建过程可能会涉及到输出xml文件，在XML文件部署之间，结果验证才是有效的xml文件。ant默认是用sax2解析器来进行对xml文件进行验证的。

The sed command gives you the power to perform these chanages on the command line,or in a shell script.sed的意思是流编辑器。它的设计初衷是对数据流进行编辑。

Blocks of code behave like anonymous functions; they have no name, and unlike functions, variables used in  blocks of code are visible outside of the function. So if you set a value to a variable in a block of code, it can be referenced outside of that block of code.

A function file simply contains all of your functions, rather than putting then in your main script. The bash command source reads in and executes whatever file you spefify. When you pass arguments to a function, the shell treats them in the same way that positional parameter arguments are treated when they are passed to commands or to the shell scripts.

The -v options tells the shell to run in verbose mode. In practice, this means that the shell will echo each command prior to executing the command.

To play with Perl, you fisrt have to install it.  To read or write files in Perl, you need to open a filehandle. File handles in Perl are yer another kind of variable. They act as convenient references between your program and the operating system about a particular file. They contain information about how the file was opened and how far along you are in reading or writing the file. They also contain user-definable attributes about how the file is to be read or written.

Hahes are another kind of collective data type. Like arrays, hashes contaion a number of scalar. The difference between arrays and hashes is that hashes access their scalar data by name, not by using a numeric subscript as arrays do. Hashes elements have two parts: a key and a value.

There are seven separate kinds of variables or variable-like things in perl:scalar variables, array variables, hash variables, subroutine names, format names, filehandles and directory hanldes.

In perl, only subroutines and formats require explicit declaration. Variables are automatically created when they are first assigned. Variables declaration comes  into play when you need to limit the scope of a variables's use. Dynamic scoping creates temporary objects within a scope. Dynamically scoped constructs are visibel globally, but only take action within their defined scopes. Dynamoc scoping applies to variables declared with local. Lexical scoping creates private constructs that are only visible within their scopes. The most frequently seen form of lexically scoped declaration is the declaration of my variables.

The printf function returns a formatted string to standard outptut,like the printf statement in c. The BEGIN pattern is followed by an action block that is executed before awk processes any lines from the input file. In fact, a BEGIN block can be tested without any input file, because awk does not start reading input until the BEGIN action block has completed. The BEGIN action is often used to change the value of the built-in variables.

END patterns do not match any input lines. The END block is executed after awk has finished processing the file.

Perl 是实用抽取和报告语言的简称，是一个用于多重特色的多面手语言。受到unix文本处理工具和shell脚本编程的启发，perl把这个特性与c语言的语法风格结合起来，从而提供了一个更为强大的开发环境。perl的核心是perl解释器，perl解释器这个引擎可以解释、编译和运行perl脚本。

三个常见的环境变量是 PATH,HOME LOGDIR。如果chdir不带参数执行的话，perl首先检查HOME的值，如果HOEM 设置了值，那么转到此目录， 如果HOME没有设置值的话，perl继续检查LOGDIR是否设置了值，如果LOGDIR也没有设置值的话，chdir命令等于什么也没做。

PERL5LIB 变量定义了类库查找的路径，那就是do require use语句所要找的目录。环境变量PERL5OPT包含了一系列命令行的可选项。PERL提供了strict程式，它增加了额外的检查一边在执行前经过编译。

chop 和chomp函数都是把字符串的最后的字符移除。包定义了变量和子程式的名称空间，package关键词可以用来定义包。


可以利用unlink函数来删除指定的文件，最好的做法是把URL的值赋值给一个变量，然后传递给delete函数来执行操作。

#!/usr/bin/perl

print "content-type: text/html \n\n"; #The header
$file = "newtext.txt";
if (unlink($file) == 0) {
    print "File deleted successfully.";
} else {
    print "File was not deleted.";
}


一次要删除多个文件，可以把要删除的文件放在一个数组里面，然后遍历这个数组，执行unlink函数操作：

#!/usr/bin/perl

print "content-type: text/html \n\n"; #The header
@files = ("newtext.txt","moretext.txt","yetmoretext.txt");
foreach $file (@files) {
    unlink($file);
}


<STDIN>表示标准输入，可以简化为<>。如果我们声明一个变量等于<STDIN>，那么这个变量的值就是我们在命令提示符输入的值。

#! usr/bin/perl
print "How old are you?";
$age = <>;
print "WOW! You are $age years old!";

perl可以执行sql操作，对MySQL数据进行增删查改，需要使用DBI模块。在安装了DBI和DBD::mysql两个模块后，可以使用use来使用这个两个模块

#!/usr/bin/perl

# PERL MODULES WE WILL BE USING
use DBI;
use DBD::mysql;

设置了数据库的platform以及数据库的名称，数据库所在的地址和端口，用户名以及密码后，使用DBI模块中的connect方法建立数据库连接。

#!/usr/bin/perl

# PERL MODULES WE WILL BE USING
use DBI;
use DBD::mysql;

# HTTP HEADER
print "Content-type: text/html \n\n";

# CONFIG VARIABLES
$platform = "mysql";
$database = "store";
$host = "localhost";
$port = "3306";
$tablename = "inventory";
$user = "username";
$pw = "password";

#DATA SOURCE NAME
$dsn = "dbi:mysql:$database:localhost:3306";


# PERL DBI CONNECT
$DBIconnect = DBI->connect($dsn, $user, $pw);



建立数据库连接后，使用prepare方法建立SQL语句的预处理，然后在执行execute方法进行数据库的查询操作。

#!/usr/bin/perl

# PERL MODULES WE WILL BE USING
use DBI;
use DBD::mysql;

# HTTP HEADER
print "Content-type: text/html \n\n";

# CONFIG VARIABLES
$platform = "mysql";
$database = "store";
$host = "localhost";
$port = "3306";
$tablename = "inventory";
$user = "username";
$pw = "password";

# DATA SOURCE NAME
$dsn = "dbi:$platform:$database:$host:$port";

# PERL DBI CONNECT
$connect = DBI->connect($dsn, $user, $pw);

# PREPARE THE QUERY
$query = "INSERT INTO inventory (id, product, quantity) VALUES (DEFAULT, 'tomatoes', '4')";
$query_handle = $connect->prepare($query);

# EXECUTE THE QUERY
$query_handle->execute();

数据库的select语句对数据库进行查询，返回数组形式的结果。

#!/usr/bin/perl

# PERL MODULES WE WILL BE USING
use DBI;
use DBD::mysql;

# HTTP HEADER
print "Content-type: text/html \n\n";

# CONFIG VARIABLES
$platform = "mysql";
$database = "store";
$host = "localhost";
$port = "3306";
$tablename = "inventory";
$user = "username";
$pw = "password";

# DATA SOURCE NAME
$dsn = "dbi:mysql:$database:localhost:3306";

# PERL DBI CONNECT
$connect = DBI->connect($dsn, $user, $pw);

# PREPARE THE QUERY
$query = "SELECT * FROM inventory ORDER BY id";
$query_handle = $connect->prepare($query);

# EXECUTE THE QUERY
$query_handle->execute();

# BIND TABLE COLUMNS TO VARIABLES
$query_handle->bind_columns(undef, \$id, \$product, \$quantity);

# LOOP THROUGH RESULTS
while($query_handle->fetch()) {
   print "$id, $product, $quantity <br />";
}