bash 在循环中填充数组
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bash populate an array in loop
提问by Dejwi
How can i populate an array in loop? I'd like to do something like that:
如何在循环中填充数组？我想做这样的事情：
declare -A results
results["a"]=1
results["b"]=2
while read data; do
results[$data]=1
done
for i in "${!results[@]}"
do
echo "key : $i"
echo "value: ${results[$i]}"
done
But it seems that I cannot add anything to an array within for loop. Why?
但似乎我无法在 for 循环中向数组添加任何内容。为什么？
回答by ruakh
What you have should work, assuming you have a version of Bash that supports associative arrays to begin with.
假设您有一个支持关联数组的 Bash 版本，那么您所拥有的应该可以工作。
If I may take a wild guess . . . are you running something like this:
如果我可以大胆猜测一下。. . 你在运行这样的东西：
command_that_outputs_keys \
| while read data; do
results[$data]=1
done
? That is — is your whileloop part of a pipeline? If so, then that's the problem. You see, every command in a pipeline receives a copyof the shell's execution environment. So the whileloop would be populating a copyof the resultsarray, and when the whileloop completes, that copy disappears.
? 也就是说——你的while循环是管道的一部分吗？如果是这样，那就是问题所在。您会看到，管道中的每个命令都会收到shell 执行环境的副本。所以while循环会填充一个副本中的results阵列，而当while循环完成，该副本消失。
Edited to add:If that isthe problem, then as glenn Hymanmanpoints out in a comment, you can fix it by using process substitutioninstead:
编辑添加：如果这是问题所在，那么正如glenn Hymanman在评论中指出的那样，您可以使用进程替换来修复它：
while read data; do
results[$data]=1
done < <(command_that_outputs_keys)
That way, although command_that_outputs_keyswill receive only a copy the shell's execution environment (as before), the whileloop will have the original, main environment, so can modify the original array.
这样，虽然command_that_outputs_keys只会收到一个 shell 执行环境的副本（和以前一样），但while循环将拥有原始的主环境，因此可以修改原始数组。
回答by icyrock.com
That seems to be working fine:
这似乎工作正常：
$ cat mkt.sh
declare -A results
results["a"]=1
results["b"]=2
while read data; do
results[$data]=1
done << EOF
3
4
5
EOF
for i in "${!results[@]}"
do
echo "key : $i"
echo "value: ${results[$i]}"
done
$ ./mkt.sh
key : a
value: 1
key : b
value: 2
key : 3
value: 1
key : 4
value: 1
key : 5
value: 1
$
Ubuntu 11.10 here, bash: GNU bash, version 4.2.10(1)-release (x86_64-pc-linux-gnu).
这里是 Ubuntu 11.10，bash：GNU bash，版本 4.2.10(1)-release (x86_64-pc-linux-gnu)。
