bash 如何在bash中为数组赋值？
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How to assign a value to an array in bash?
提问by jordanm
I am trying to read a list of values from a text file hello.txt and store them in an array.
我正在尝试从文本文件 hello.txt 读取值列表并将它们存储在数组中。
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 ${Unix_Array[2]}
I am not able to assign values to the array Unix_Array[].. The echo statement does not print the contents of the array.
我无法为数组 Unix_Array[] 赋值。 echo 语句不打印数组的内容。
回答by kojiro
There are a few syntax errors here, but the clear problem is that the assignments are happening, but you're in an implied subshell. By using a pipe, you've created a subshell for the entire while statement. When the while statement is done the subshell exits and your Unix_Arrayceases to exist.
这里有一些语法错误，但明显的问题是分配正在发生，但您处于隐含的 subshell 中。通过使用管道，您已经为整个 while 语句创建了一个子 shell。当while语句完成时，子shell退出并且您的Unix_Array不复存在。
In this case, the simplest fix is not to use a pipe:
在这种情况下，最简单的解决方法是不使用管道：
counter=0
while read line; do
Unix_Array[$counter]=$line;
let counter=counter+1;
echo $counter;
done < hello.txt
echo ${Unix_Array[0]}
echo ${Unix_Array[1]}
echo ${Unix_Array[2]}
By the way, you don't really need the counter. An easier way to write this might be:
顺便说一下，你真的不需要计数器。一种更简单的写法可能是：
$ 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 "${#some_array[@]}" # Get the length of the array
4
回答by jordanm
If you are using bash v4 or higher, you can use mapfileto accomplish this:
如果您使用的是 bash v4 或更高版本，您可以使用它mapfile来完成此操作：
mapfile -t Unix_Array < hello.txt
Otherwise, this should work:
否则，这应该有效：
while read -r line; do
Unix_Array+=("$line")
done < hello.txt
回答by Arthur Alves
Its a solution:
它的一个解决方案：
count=0
Unix_Array=($(cat hello.txt))
array_size=$(cat hello.txt | wc -l)
for ((count=0; count < array_size; count++))
do
echo ${Unix_Array[$count]}
done
回答by Alex
The best way I found is:
我发现的最好方法是：
declare -A JUPYTER_VENV
JUPYTER_VENV=(test1 test2 test3)
And then consume it with:
然后使用它：
for jupenv in ${JUPYTER_ENV[@]}
do
echo $jupenv
done
回答by Jon Lin
Instead of this:
取而代之的是：
cat hello.txt | while read line; do
${Unix_Array[${counter}]}=$line;
let counter=counter+1;
echo $counter;
done
You can just do this:
你可以这样做：
Unix_Array=( `cat "hello.txt" `)
