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gawk中的字符串数字(STRNUM)介绍

2019年03月25日  | 移动技术网科技  | 我要评论

几天前在论坛看到一个帖子 这是个挺有意思的问题。
我自己做了几个试验，发现00e1有这个问题，但是00a1、00b1、00c1等其它字符串却没有这个问题。

前天，怀着忐忑的心情给 bug-gawk@gnu.org 发了一封邮件：

[bug report] gawk doesn’t work correctly when assign special value to variable
to: bug-gawk@gnu.org

1. symptom:
gawk doesn’s work correctly when assign special value (like 00e1) variable.

2. steps to repeat this issue:

1) download and compile the latest gawk 4.1.3
http://ftp.gnu.org/gnu/gawk/
[root]# gawk --version | head -2
gnu awk 4.1.3, api: 1.1
copyright (c) 1989, 1991-2015 free software foundation.

2) prepare a test file
cat > 1.txt << eof
00e1 00e1
00e2 00e4
00e3 00e1_01
eof

3) execute following command to see the result
[root]# gawk -v var="00e1" '$2==var' 1.txt
00e1 00e1
00e2 00e4

the second line should not be there. because "00e4" is not equal to "00e1" obviously.
is it a bug or by design?

3. workaround:
gawk -v var="00e1" '$2==""var' 1.txt
gawk -v var="^00e1___fckpd___0quot; '$2~var' 1.txt

没想到，昨天就收到了来自 andrew j. schorr 大神的回复，效率还真是高呢，32个赞：

on thu, aug 06, 2015 at 03:55:50pm +0800, shell_hat wrote:
> the second line should not be there. because "00e4" is not equal to "00e1" obviously.
> is it a bug or by design?

this is a tricky area. please check the manual for the discussion of "string type versus numeric type":
http://www.gnu.org/software/gawk/manual/html_node/variable-typing.html

i think the command-line assignment results in a variable of type strnum.

> 3. workaround:
> gawk -v var="00e1" '$2==""var' 1.txt
> gawk -v var="^00e1___fckpd___1quot; '$2~var' 1.txt

these examples may also be helpful:

bash-4.2$ gawk 'begin {var = "00e1"} $2 == var' 1.txt
00e1 00e1
bash-4.2$ gawk 'begin {var = 00e1} $2 == var' 1.txt
00e1 00e1
00e2 00e4

regards,
andy

看完那篇文档，似有所悟。但是还是没搞清楚为啥00a1、00b1、00c1等字符串没问题呢？
喝完一杯咖啡之后，恍然大悟：科学计数法！泥煤的~~~

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