gawk中的字符串数字(STRNUM)介绍

[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

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