Bash 未绑定变量数组（脚本：s3-bash）

Question

我正在使用：s3-bash，当我在我的本地环境中运行它时 (OS X 10.10.1) 我没有任何问题，当我尝试运行它在 ubuntu server 14.04.1 我收到以下错误：

./s3-common-functions: line 66: temporaryFiles: unbound variable
./s3-common-functions: line 85: temporaryFiles: unbound variable

我查看了 s3-common-functions 脚本，变量看起来已正确初始化（作为数组）：

# Globals
declare -a temporaryFiles

但是评论里有个备注，我确定是不是相关的：

# Do not use this from directly. Due to a bug in bash, array assignments do not work when the function is used with command substitution
function createTemporaryFile
{
    local temporaryFile="$(mktemp "$temporaryDirectory/$$..XXXXXXXX")" || printErrorHelpAndExit "Environment Error: Could not create a temporary file. Please check you /tmp folder permissions allow files and folders to be created and disc space." $invalidEnvironmentExitCode
    local length="${#temporaryFiles[@]}"
    temporaryFiles[$length]="$temporaryFile"
}

Answer 1

更改了 temporaryfiles

的数组声明

declare -a temporaryFiles

至：

temporaryFiles=()

为什么这在 ubuntu 14.04.1 Linux 3.13.0-32-generic x86_64 和 OS X 中不同/不起作用我不确定？

Answer 2

这里似乎有一个 bash 行为改变。

小次郎发现：CHANGES

hhhh. Fixed a bug that caused `declare' and `test' to find variables that had been given attributes but not assigned values. Such variables are not set.

$ bash --version
GNU bash, version 3.2.25(1)-release (x86_64-redhat-linux-gnu)
Copyright (C) 2005 Free Software Foundation, Inc.
$ set -u
$ declare -a tF
$ echo "${#tF[@]}"
0

对比

$ bash --version
GNU bash, version 4.1.2(1)-release (x86_64-redhat-linux-gnu)
Copyright (C) 2009 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>

This is free software; you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
$ set -u
$ declare -a tF
$ echo "${#tF[@]}"
0

对比

$ bash --version
GNU bash, version 4.3.30(1)-release (x86_64-pc-linux-gnu)
Copyright (C) 2013 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>

This is free software; you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
$ set -u
$ declare -a tF
$ echo "${#tF[@]}"
-bash: tF: unbound variable

您可以在较新的 bash 版本上使用 declare -a tF=() 来解决这个问题。

$ declare -a tF=()
$ echo "${#tF[@]}"
0

Answer 3

Bash 可以使用破折号将空值替换为未设置的变量。

set -u
my_array=()
printf "${my_array[@]-}\n"

这个具体的例子不会打印任何东西，但它也不会给你一个未绑定的变量错误。

Stolen from here

Answer 4

find $fullfolder -type f |
while read fullfile
do
    filename=$(basename "$fullfile")
    ext=$([[ $filename = *.* ]] && printf %s ${filename##*.} || printf 'NONE')
    arr+=($ext)
    echo ${#arr[@]}
done
echo ${#arr[@]}

为什么for循环里面的${#arr[@]}结果是正确的，而外面的结果是0？

Bash 未绑定变量数组（脚本：s3-bash）

Bash unbound variable array (script: s3-bash)

bash