Re: weird behaviour of ((count++)) when using , , to change to lower case
On 8/1/10 7:05 PM, Dennis Williamson wrote: > If I do the echo line twice, I get a segfault in both Bash > 4.0.33(1)-release and 4.1.0(1)-release. Thanks. This will be fixed in bash-4.2. > And you're right about being evaluated twice. This was already changed after bash-4.1 was released; the change will be in bash-4.2. Chet -- ``The lyf so short, the craft so long to lerne.'' - Chaucer ``Ars longa, vita brevis'' - Hippocrates Chet Ramey, ITS, CWRUc...@case.eduhttp://cnswww.cns.cwru.edu/~chet/
Re: weird behaviour of ((count++)) when using , , to change to lower case
If I do the echo line twice, I get a segfault in both Bash
4.0.33(1)-release and 4.1.0(1)-release.
And you're right about being evaluated twice.
On Sun, Aug 1, 2010 at 3:59 PM, Bernd Eggink wrote:
> Am 01.08.2010 13:06, schrieb Andrew Benton:
>
>> Also good. Now try converting it to lower case with ,,
>>
>> andy:~$ count=0
>> andy:~$ echo "${days[${count}],,}, ${days[$((count++))],,},
>> ${days[$((count++))],,}"
>> monday, tuesday, thursday
>>
>> What happened to wednesday?
>
> I'd rather expect this to print "monday, monday, tuesday", since you left
> out the ++ in the first term.
>
> I think the problem is that the ,, operator causes each expression to be
> evaluated twice. That would explain this behaviour, and it's a bug IMHO.
>
> Regards,
> Bernd
>
> --
> Bernd Eggink
> http://sudrala.de
>
>
Re: weird behaviour of ((count++)) when using , , to change to lower case
Am 01.08.2010 13:06, schrieb Andrew Benton:
Also good. Now try converting it to lower case with ,,
andy:~$ count=0
andy:~$ echo "${days[${count}],,}, ${days[$((count++))],,},
${days[$((count++))],,}"
monday, tuesday, thursday
What happened to wednesday?
I'd rather expect this to print "monday, monday, tuesday", since you
left out the ++ in the first term.
I think the problem is that the ,, operator causes each expression to be
evaluated twice. That would explain this behaviour, and it's a bug IMHO.
Regards,
Bernd
--
Bernd Eggink
http://sudrala.de
weird behaviour of ((count++)) when using , , to change to lower case
Configuration Information [Automatically generated, do not change]:
Machine: x86_64
OS: linux-gnu
Compiler: gcc
Compilation CFLAGS: -DPROGRAM='bash' -DCONF_HOSTTYPE='x86_64'
-DCONF_OSTYPE='linux-gnu' -DCONF_MACHTYPE='x86_64-unknown-linux-gnu'
-DCONF_VENDOR='unknown' -DLOCALEDIR='/usr/share/locale' -DPACKAGE='bash'
-DSHELL -DHAVE_CONFIG_H -I. -I. -I./include -I./lib -g -O2
uname output: Linux eccles 2.6.35-rc6 #1 SMP Fri Jul 23 11:52:29 BST 2010
x86_64 x86_64 x86_64 GNU/Linux
Machine Type: x86_64-unknown-linux-gnu
Bash Version: 4.1
Patch Level: 2
Release Status: release
Description:
Incrementing a variable with ((count++)), which should access the value
in the variable and then increment it by 1 has some strange behaviour.
In some situations it seems to increment the variable before accessing
it, and in others it increments it by 2
Repeat-By:
Make an array to work with:
andy:~$ days=({Mon,Tues,Wednes,Thurs,Fri,Satur,Sun}day)
andy:~$ echo ${da...@]}
Monday Tuesday Wednesday Thursday Friday Saturday Sunday
So far, so good. Now try to access the array by stepping through it with
((count++))
andy:~$ count=0
andy:~$ echo "${days[$((count++))]}, ${days[$((count++))]},
${days[$((count++))]}"
Monday, Tuesday, Wednesday
Also good. Now try converting it to lower case with ,,
andy:~$ count=0
andy:~$ echo "${days[${count}],,}, ${days[$((count++))],,},
${days[$((count++))],,}"
monday, tuesday, thursday
What happened to wednesday?
Andy
