问题描述
运行这些命令给了预期的效果。
Running these commands gives expected results
$ bash --version
GNU bash, version 4.1.11(2)-release
$ foo=(111 222 333)
$ IFS=, cat <<< "${foo[*]}"
111,222,333
但它似乎与猛砸4.2 IFS值被忽略
However it appears with Bash 4.2 the IFS value is being ignored
$ bash --version
GNU bash, version 4.2.0(1)-release
$ foo=(111 222 333)
$ IFS=, cat <<< "${foo[*]}"
111 222 333
是什么导致了这种差异？
What is causing this difference?
我找到了答案在这里
看起来好像这一直都是一个错误。据切特
重定向不应该接触到TEMP环境
（ IFS 在这种情况下）
It looks as though this has been an error all along. According to Chet,redirections should never have had access to the temp environment(IFS in this case)
推荐答案
我觉得4.2正确的，因为分词的行为应该分配的评估之前，首先发生了：
I find the behaviour of 4.2 correct as word splitting should happen first before evaluation of assignments:
IFS=, cat <<< "${foo[*]}"
我相信IFS的新值只会影响猫，而不是＆LT;＆LT;＆LT; $ {foo的[*]}。
要做到这一点，正确的方法是
The proper way to do that is
IFS=, eval 'cat <<< "${foo[*]}"'
而对于保守的方法，我们可以使用一个函数：
And for a conservative approach we can use a function:
function t { cat <<< "${foo[*]}"; }
IFS=, t
我也有猜测，它是与此相关的：
I also have a guess that it's related to this:
m. Fixed a bug that caused here documents to not be displayed correctly
when attached to commands inside compound commands.
更新
另一个令人困惑的行为可在4.2这已经是固定在4.3中找到。通过这样做 IFS =，猫＆LT;＆LT;＆LT; $ {foo的[*]}，$ {foo的[*]}扩大以及111 222 333（不受IFS），通过猫是 111 222 333 。然而，当我们做 IFS =读巴≤;＆LT;＆LT; $ {foo的[*]};回声$栏，输出会 111222333 键，会出现，如果$ {foo的[*]} 扩展为111222333。这种不一致的行为已不再猛砸4.3发生和Bash 4.3的行为可能是一个修补程序。
Update
Another confusing behavior can be found in 4.2 which is already fixed in 4.3. By doing IFS=, cat <<< "${foo[*]}", "${foo[*]}" expands well as "111 222 333" (not affected by IFS) as shown by cat which is 111 222 333. However when we do IFS=, read bar <<< "${foo[*]}"; echo "$bar", the output would be 111,222,333 and would appear as if "${foo[*]}" expanded as "111,222,333". This inconsistent behavior is no longer happening in Bash 4.3 and Bash 4.3's behavior is probably a fix.
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