gawk如何判断字段的类型?

gawk如何判断字段的类型?

gawk如何判断字段的类型?是字符型还是数值型?      
用正则表达式呗      
如何一个字符串中首字母是数字,并且由数字和字母组成,如何判断?      
^[0-9][[:alnum:]]*$      
我觉得自定义一个type()函数较好.      
有这必要么
man bash
search for class      
能举个例子吗????      
前面的 [[:alnum:]] 就是一个 character class      
man from awk
引用:
[:alnum:]  Alphanumeric characters.re hexa

       [:alpha:]  Alphabetic characters.

       [:blank:]  Space or tab characters.

       [:cntrl:]  Control characters.

       [:digit:]  Numeric characters.

       [:graph:]  Characters  that  are  both  printable  and  visible.  (A space is printable, but not visible, while an a is
                  both.)

       [:lower:]  Lower-case alphabetic characters.

       [:print:]  Printable characters (characters that are not control characters.)

       [:punct:]  Punctuation characters (characters that are not letter, digits, control characters, or space characters).

       [:space:]  Space characters (such as space, tab, and formfeed, to name a few).

       [:upper:]  Upper-case alphabetic characters.

       [:xdigit:] Characters that are hexadecimal digits.
      
LZ 是指類(class), 物件導向的方式?
根據 sed & awk 第七章所述 ,awk
變量不必聲明, awk 每個變量會有一個
字符和數字類型,awk會根據表示式的
前後關係來取得合適的類型      
journalist