gawk中的字符串数字(STRNUM)介绍
几天前在论坛看到一个帖子 http://bbs.chinaunix.net/thread-4184581-1-1.html 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 variableTo: bug-gawk@gnu.org1. 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 4.1.3http://ftp.gnu.org/gnu/gawk/[root]# gawk --version | head -2GNU Awk 4.1.3, API: 1.1Copyright (C) 1989, 1991-2015 Free Software Foundation.2) Prepare a test filecat > 1.txt << EOF00e1 00e100e2 00e400e3 00e1_01EOF3) Execute following command to see the result[root]# gawk -v var="00e1" '$2==var' 1.txt00e1 00e100e2 00e4The 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.txtgawk -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.htmlI 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; '$2~var' 1.txtThese examples may also be helpful:bash-4.2$ gawk 'BEGIN {var = "00e1"} $2 == var' 1.txt00e1 00e1bash-4.2$ gawk 'BEGIN {var = 00e1} $2 == var' 1.txt00e1 00e100e2 00e4Regards,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~~~