perl语言中的q系列符号用法(q_qq_qr_qw_qx)
2010-09-17 16:49:57 
阿炯
有如下一些q的用法:
* q - singly quote a string
* qq - doubly quote a string
* qr - Compile pattern
* qw - quote a list of words
* qx - backquote quote a string
q// is generally the same thing as using single quotes - meaning it doesn't interpolate values inside the delimiters.
qq// is the same as double quoting a string. It interpolates.
qw// return a list of white space delimited words. @q = qw/this is a test/ is functionally the same as @q = ('this', 'is', 'a', 'test')
qx// is the same thing as using the backtick operators.
I've never used qr//, but it's got something to do with compiling regex's for later use.
在perl语言中，有两个特殊而常用的符号qq qw,分别解释如下:
qq{foobar}的意思为意思为双引号字符串，可内插变量，相当于 "foobar"
qw{foo bar}的意思为用空格分解字符串，得到列表，相当于如下语句:
split(' ','foo bar') 得到的结果是'foo','bar'
字符串比较等于用 eq
q运算符对'号转义的方式:
$someword = 'i \'ve some money';
可以等价于:
$someword = q~i 've some money~;
qq运算符对"号转义的方式
$someword = "i say \"ok!\".";
可以等价于:
$someword = qq~i say "ok!".~;
qw代表用空格来分隔元素,得到列表
@list = ("perl","Regular","network","web");
可以等价于:
@list = qw(perl Regular network web);
qr代表创建正则
$myword = "cnangel";
$replaceword = qr(cnangel);
$finalword = "ok" if ($myword =~ $replaceword);
引号执行运算符(quoted execution operator)，qx//
qx/uname -p -r/
q 和 qq 运算符的特点:
※ q 和 qq 必须是一个标识符，而不是标识符的部分。例如:
q (abc) 用 () 作为分界符
q(abc) 用 () 作为分界符
q xabcx 用 x 作为分界符
都是合法的，而 qxabcx 就会被当作是一个标识符来处理，有谁会想到 qxabcx 居然是一个 q 运算式呢？
q 和 qq 后面的空格并不会影响语法，但是任何非空字符(不是空格、不是 TAB 字符、不是换行符)则会被当作界限符来使用。
如果 q 和 qq 使用一些特殊的符号的时候，则必须配对。比如:; 在一起用来当作界限符，而不能只用两个 < 作为界限符。而 | 则只能和它自己作为一对界限符。这些特殊的符号有:()、{}、[]、;
$myword = "cnangel";
$replaceword = qr(cnangel);
$finalword = "ok" if ($myword =~ $replaceword);
@list = ("perl","Regular","network","web");
可以等价于:
@list = qw(perl Regular network web);
$someword = 'i \'v some money';
可以等价于:
$someword = q~i 'v some money~;
qr quotes its STRING as a regular expression. STRING is interpolated the same way as PATTERN in m/PATTERN/.
Syntax
qr EXPR
Return Value
This function returns a Perl value which may be used instead of the corresponding /STRING/ expression.
Example
$rex = qr/my.STRING/is;
s/$rex/foo/;
Is equivalent to
s/my.STRING/foo/is;
When above code is executed, it produces the following result
$re = qr/$pattern/;
$string =~ /foo${re}bar/; # can be interpolated in other patterns
$string =~ $re; # or used standalone
$string =~ /$re/; # or this way
* q - singly quote a string
* qq - doubly quote a string
* qr - Compile pattern
* qw - quote a list of words
* qx - backquote quote a string
q// is generally the same thing as using single quotes - meaning it doesn't interpolate values inside the delimiters.
qq// is the same as double quoting a string. It interpolates.
qw// return a list of white space delimited words. @q = qw/this is a test/ is functionally the same as @q = ('this', 'is', 'a', 'test')
qx// is the same thing as using the backtick operators.
I've never used qr//, but it's got something to do with compiling regex's for later use.
在perl语言中，有两个特殊而常用的符号qq qw,分别解释如下:
qq{foobar}的意思为意思为双引号字符串，可内插变量，相当于 "foobar"
qw{foo bar}的意思为用空格分解字符串，得到列表，相当于如下语句:
split(' ','foo bar') 得到的结果是'foo','bar'
字符串比较等于用 eq
q运算符对'号转义的方式:
$someword = 'i \'ve some money';
可以等价于:
$someword = q~i 've some money~;
qq运算符对"号转义的方式
$someword = "i say \"ok!\".";
可以等价于:
$someword = qq~i say "ok!".~;
qw代表用空格来分隔元素,得到列表
@list = ("perl","Regular","network","web");
可以等价于:
@list = qw(perl Regular network web);
qr代表创建正则
$myword = "cnangel";
$replaceword = qr(cnangel);
$finalword = "ok" if ($myword =~ $replaceword);
引号执行运算符(quoted execution operator)，qx//
qx/uname -p -r/
q 和 qq 运算符的特点:
※ q 和 qq 必须是一个标识符，而不是标识符的部分。例如:
q (abc) 用 () 作为分界符
q(abc) 用 () 作为分界符
q xabcx 用 x 作为分界符
都是合法的，而 qxabcx 就会被当作是一个标识符来处理，有谁会想到 qxabcx 居然是一个 q 运算式呢？
q 和 qq 后面的空格并不会影响语法，但是任何非空字符(不是空格、不是 TAB 字符、不是换行符)则会被当作界限符来使用。
如果 q 和 qq 使用一些特殊的符号的时候，则必须配对。比如:; 在一起用来当作界限符，而不能只用两个 < 作为界限符。而 | 则只能和它自己作为一对界限符。这些特殊的符号有:()、{}、[]、;
$myword = "cnangel";
$replaceword = qr(cnangel);
$finalword = "ok" if ($myword =~ $replaceword);
@list = ("perl","Regular","network","web");
可以等价于:
@list = qw(perl Regular network web);
$someword = 'i \'v some money';
可以等价于:
$someword = q~i 'v some money~;
qr quotes its STRING as a regular expression. STRING is interpolated the same way as PATTERN in m/PATTERN/.
Syntax
qr EXPR
Return Value
This function returns a Perl value which may be used instead of the corresponding /STRING/ expression.
Example
$rex = qr/my.STRING/is;
s/$rex/foo/;
Is equivalent to
s/my.STRING/foo/is;
When above code is executed, it produces the following result
$re = qr/$pattern/;
$string =~ /foo${re}bar/; # can be interpolated in other patterns
$string =~ $re; # or used standalone
$string =~ /$re/; # or this way