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gawk中的字符串数字(STRNUM)介绍

  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 corr...

  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: gawk中的字符串数字(STRNUM)介绍

  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~~~