如何在bash中为数组分配值？ [英] How to assign a value to an array in bash?

问题描述

我正在尝试从文本文件hello.txt中读取值列表，并将它们存储在数组中。

I am trying to read a list of values from a text file hello.txt and store them in an array.

counter=0

cat hello.txt | while read line; do
 ${Unix_Array[${counter}]}=$line;
 let counter=counter+1;
    echo $counter;
done

echo ${Unix_Array[0]}
echo ${Unix_Array[1]}
echo ${Unix_Array[2]}

我无法为数组Unix_Array []分配值。echo语句不打印数组的内容。

I am not able to assign values to the array Unix_Array[].. The echo statement does not print the contents of the array.

推荐答案

此处存在一些语法错误，但很明显的问题是分配正在发生，但是您位于隐含的子外壳中。通过使用管道，您已经为整个while语句创建了一个子外壳。 while语句完成后，子shell退出，您的 Unix_Array 不再存在。

There are a few syntax errors here, but the clear problem is that the assignments are happening, but you're in an implied subshell. By using a pipe, you've created a subshell for the entire while statement. When the while statement is done the subshell exits and your Unix_Array ceases to exist.

在这种情况下，最简单的解决方法是不使用管道：

In this case, the simplest fix is not to use a pipe:

counter=0

while read line; do
  Unix_Array[$counter]=$line;
  let counter=counter+1;
  echo $counter;
done < hello.txt

echo ${Unix_Array[0]}
echo ${Unix_Array[1]}
echo ${Unix_Array[2]}

顺便说一句，您真的不需要计数器。

By the way, you don't really need the counter. An easier way to write this might be:

$ oIFS="$IFS" # Save the old input field separator
$ IFS=$'\n'   # Set the IFS to a newline
$ some_array=($(<hello.txt)) # Splitting on newlines, assign the entire file to an array
$ echo "${some_array[2]}" # Get the third element of the array
c
$ echo "${#some_array[@]}" # Get the length of the array
4

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