bash 数组的前缀和后缀元素
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Prefix and postfix elements of a bash array
提问by Erik
I want to pre- and postfix an array in bash similar to brace expansion.
我想在 bash 中前缀和后缀类似于括号扩展的数组。
Say I have a bash array
说我有一个 bash 数组
ARRAY=( one two three )
I want to be able to pre- and postfix it like the following brace expansion
我希望能够像下面的大括号扩展一样对其进行前缀和后缀
echo prefix_{one,two,three}_suffix
The best I've been able to find uses bash regex to either add a prefix or a suffix
我能找到的最好的使用 bash regex 添加前缀或后缀
echo ${ARRAY[@]/#/prefix_}
echo ${ARRAY[@]/%/_suffix}
but I can't find anything on how to do both at once. Potentially I could use regex captures and do something like
但我找不到任何关于如何同时做到这两点的信息。可能我可以使用正则表达式捕获并执行类似的操作
echo ${ARRAY[@]/.*/prefix__suffix}
but it doesn't seem like captures are supported in bash variable regex substitution. I could also store a temporary array variable like
但 bash 变量正则表达式替换似乎不支持捕获。我还可以存储一个临时数组变量，如
PRE=(${ARRAY[@]/#/prefix_})
echo ${PRE[@]/%/_suffix}
This is probably the best I can think of, but it still seems sub par. A final alternative is to use a for loop akin to
这可能是我能想到的最好的，但它似乎仍然低于标准。最后一种选择是使用类似于
EXPANDED=""
for E in ${ARRAY[@]}; do
EXPANDED="prefix_${E}_suffix $EXPANDED"
done
echo $EXPANDED
but that is super ugly. I also don't know how I would get it to work if I wanted spaces anywhere the prefix suffix or array elements.
但这太丑了。如果我想在前缀后缀或数组元素的任何地方使用空格，我也不知道如何让它工作。
回答by Arthur2e5
Bash brace expansion don't use regexes. The pattern used is just some shell glob, which you can find in bash manual 3.5.8.1 Pattern Matching.
Bash 大括号扩展不使用正则表达式。使用的模式只是一些 shell glob，您可以在 bash 手册3.5.8.1 Pattern Matching 中找到它。
Your two-step solution is cool, but it needs some quotes for whitespace safety:
您的两步解决方案很酷，但它需要一些引号以确保空格安全：
ARR_PRE=("${ARRAY[@]/#/prefix_}")
echo "${ARR_PRE[@]/%/_suffix}"
You can also do it in some evil way:
你也可以用一些邪恶的方式来做：
eval "something $(printf 'pre_%q_suf ' "${ARRAY[@]}")"
回答by John Kugelman
Your last loop could be done in a whitespace-friendly way with:
您的最后一个循环可以以对空格友好的方式完成：
EXPANDED=()
for E in "${ARRAY[@]}"; do
EXPANDED+=("prefix_${E}_suffix")
done
echo "${EXPANDED[@]}"
回答by Niklas Holm
Prettier but essentially the same as the loop solution:
更漂亮但本质上与循环解决方案相同：
$ ARRAY=(A B C)
$ mapfile -t -d $'ARRAY=( one two three )
(IFS=,; eval echo prefix_\{"${ARRAY[*]}"\}_suffix)
' EXPANDED < <(printf "prefix_%s_postfixSTRING="one two three"
eval echo prefix_\{${STRING// /,}\}_suffix
" "${ARRAY[@]}")
$ echo "${EXPANDED[@]}"
prefix_A_postfix prefix_B_postfix prefix_C_postfix
mapfilereads rows into elements of an array. With -d $'\0'it instead reads null-delimited strings and -tomits the delimiter from the result. See help mapfile.
mapfile将行读入数组元素。-d $'\0'而是使用它读取空分隔的字符串并-t从结果中省略分隔符。见help mapfile。
回答by Ryba
For arrays:
对于数组：
echo prefix_{one,two,three}_suffix
For strings:
对于字符串：
echo ${${ARRAY[@]/#/prefix_}/%/_suffix}
evalcauses its arguments to be evaluated twice, in both cases first evaluation results in
eval导致其参数被评估两次，在这两种情况下，第一次评估都会导致
myarray=( one two three )
newarray=( $(echo ${myarray[*]}|sed "s/\(\b[^ ]\+\)/pre--post/g") )
echo ${newarray[@]}
> pre-one-post pre-two-post pre-three-post
echo ${#newarray[@]}
> 3
and second executes it. For array case subshell is used to avoid overwiting IFS
然后第二个执行它。对于数组 case 子shell 用于避免覆盖 IFS
You can also do this in zsh:
您也可以在 zsh 中执行此操作：
##代码##回答by bruin
I have exactly the same question, and I come up with the following solution using sed's word boundary match mechanism:
我有完全相同的问题，我使用 sed 的字边界匹配机制提出了以下解决方案：
##代码##Waiting for more elegant solutions...
等待更优雅的解决方案......
