linux - 如何在for循环中调用变量作为变量名和变量值

Question

我对 Linux 中的脚本编写相对较新(更习惯于使用 R)，但我正在尝试执行一个脚本，在该脚本中我将一些变量设置为文件路径，然后我可以随后在 for 循环中调用它们，所以我可以调用两者脚本中的变量名和变量值。

例如，我将为命令的参数调用变量值(如在文件路径中)，但对于命令的输出，我将调用变量名来写入输出。我试图使用下面的花括号来实现这一点。这行得通吗？？？

如有任何帮助，我们将不胜感激!

#Generate variables with path directories
C1=/path/file1
C2=/path/file2
C3=/path/file3
C4=/path/file4
L1=/path/file1
L2=/path/file2
L3=/path/file3

#Loop through each instance of C for each instance of L (to create L*C number of outputs)
for Cid in C1, C2, C3, C4,
do for Lid in L1, L2, L3,
do
commandA -arg1 $${Cid} -arg2 $${Lid} -output /path/file${Cid}${Lid}
done
done

Answer 1

这是用declare -A声明的关联数组的工作:

#!/usr/bin/env bash

declare -A arr=(
[C1]=/path/file1
[C2]=/path/file2
[L1]=/path/file1
[L2]=/path/file2
)

for index in "${!arr[@]}"; do
    echo "$index:${arr[$index]}"
done

• ${!arr[@]}:数组的所有索引(C1, C2, ...)
• ${arr[$index]}:给定索引对应的数组元素(/path/file1, ...)

---

如果你想坚持使用常规变量，你可以使用variable indirection :

C1=/path/file1
C2=/path/file2
L1=/path/file1
L2=/path/file2

for var in C1 C2 L1 L2; do
    echo "$var:${!var}"
done

${!parameter}

If the first character of parameter is an exclamation point (!), and parameter is not a nameref, it introduces a level of variable indirection. Bash uses the value of the variable formed from the rest of parameter as the name of the variable; this variable is then expanded and that value is used in the rest of the substitution, rather than the value of parameter itself.