條件式中的語法錯誤

Question

我正在編寫一個腳本，其中使用邏輯“OR”和邏輯“AND”語句的組合。這是腳本：

#!/bin/bash

echo "Enter the value of a"
read $a
echo "Enter the value of b"
read $b
if

[[ $a != STARTED && $b == STARTED ] || [ $b != STARTED && $a == STARTED ]]; then

echo "Either of the JVMs is not yet up, so lets wait for some more time"

i=$(($i+1))
sleep 1s

fi

並在執行時出現以下錯誤：

line 13: syntax error in conditional expression
line 13: syntax error near `]'
line 13: `[[ $a != STARTED && $b == STARTED ] || [ $b != STARTED && $a == STARTED ]]; then'

我正在使用 bash shell。非常感謝對此的任何幫助。

Answer 1

您[[與不匹配]。應始終以和with[[關閉。使用：]][]

if [[ $a != STARTED && $b == STARTED ]] || [[ $b != STARTED && $a == STARTED ]]; then

更好的是，因為你[[無論如何都在使用：

if [[ ($a != STARTED && $b == STARTED) || ($b != STARTED && $a == STARTED) ]]; then

另一個錯誤是您在執行以下操作，直到應用格式後我才注意到：

read $a
read $b

你應該這樣做：

read a
read b

對於第一種形式，$a和$b被 shell 替換為它們的內容，所以如果您沒有在此行之前設定它們，最終的命令將是：

read

（在這種情況下，讀取的值將儲存在變數中REPLY。）如果您設定了a某些值（例如a="blah blah"），則它看起來像：

read blah blah

Answer 2

代替：

[[ $a != STARTED && $b == STARTED ] || [ $b != STARTED && $a == STARTED ]]; then

我會用：

if [ $a != STARTED && $b == STARTED ] || [ $b != STARTED && $a == STARTED ]; then