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Re: IFS is ignored when concatenating array elements


From: isabella parakiss
Subject: Re: IFS is ignored when concatenating array elements
Date: Sun, 15 Mar 2015 13:07:43 +0100

On 3/14/15, Le Manh Cuong <address@hidden> wrote:
> In bash, you need to quote in second arr assignment:
> $ arr=(a b c); IFS=+; arr="${arr[*]/a/x}"; echo "$arr"x+b+c
> A note that the result from those shells are different. After second
> assignment to arr:
> - In bash and ksh, arr still be an array, contain 3 elements "x b c", "b",
> "c"
> ==bash== $ typeset | grep arr arr=([0]="x+b+c" [1]="b" [2]="c")
> ==ksh==$ typeset | grep arrindexed array
> - In zsh and yash, arr now is a string:
> ==zsh==$ typeset | grep arrarr=x+b+c
> ==yash==
> $ typeset | grep arrtypeset arr='x+b+c'
> -- Mr. LE Manh CuongMobile: +84 1216 181090Skype: manhcuongle> Date: Fri, 13
> Mar 2015 23:15:43 +0100
>> Subject: IFS is ignored when concatenating array elements
>> From: address@hidden
>> To: address@hidden
>>
>> This works as I would expect:
>>
>> $ arr=(a b c); IFS=+; echo "${arr[*]/a/x}"
>> x+b+c
>>
>>
>> But for some reason, this ignores IFS:
>>
>> $ arr=(a b c); IFS=+; arr=${arr[*]/a/x}; echo "$arr"
>> x b c
>>
>>
>>
>>
>> Here is the behaviour of other shells that allow that kind of syntax:
>>
>>    input: arr=(a b c); IFS=+; echo "${arr[*]/a/x}"
>> =======================
>>     bash: x+b+c
>>      ksh: x+b+c
>>     yash: x+b+c
>>      zsh: x+b+c
>>
>>    input: arr=(a b c); IFS=+; arr=${arr[*]/a/x}; echo "$arr"
>> =======================
>>     bash: x b c
>>      ksh: x+b+c
>>     yash: x+b+c
>>      zsh: x+b+c
>>
>                                       

(I'm sending your message to the mailing list too)

Well, I just find it weird that quotes aren't needed in this case:
$ arr=(a b c); IFS=+; arr=${arr[*]}; echo "$arr"
a+b+c

but they are in this case:
$ arr=(a b c); IFS=+; arr=${arr[*]/a/x}; echo "$arr"
x b c

But apparently that's a recent addition, since 4.2 and below still
ignore IFS:

4.2$ arr=(a b c); IFS=+; arr=${arr[*]}; echo "$arr"
a b c

I just thought it would be nice to have a consistent behaviour.


---
xoxo, iza



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