Bash 错误：“第 8 行：[: 2：应为一元运算符”
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Bash error: "line 8: [: 2: unary operator expected"
提问by ElenaD
Please help me with this error I received with a shell script in Bash:
line 8: [: 2: unary operator expected
请帮助我解决我在 Bash 中使用 shell 脚本收到的错误：
line 8: [: 2: unary operator expected
#!/bin/bash
echo "Input your number for factorial calculation: "
read $nr
counter=2
factorial=1
while [ $counter -le $nr ]
do
factorial=$(( $factorial * $counter ))
counter=$(( $counter + 1 ))
done
echo "The result " $nr "! is:"
echo $factorial
Something is wrong with the while line. Maybe the $nris not used correctly?
while 行出了点问题。也许$nr没有正确使用？
回答by gudok
readtakes nameof the variable, not its value. You need to replace read $nrwith read nr.
read获取变量的名称，而不是它的值。您需要替换read $nr为read nr.
回答by Mort
You seem to be having trouble formatting your question, so I cannot see it, but generally you get that error if you have something like if [ $a -ne $b ]but one of $aor $bis empty, so basically the interpreter sees something like if [ -ne $b ]. They ways to avoid it are either
您似乎在格式化您的问题时遇到问题，所以我看不到它，但通常如果您有类似if [ $a -ne $b ]但其中之一$a或$b为空的内容，您会收到该错误，因此基本上解释器会看到类似if [ -ne $b ]. 他们避免它的方法是
- Ensure that the variables are set before such a test, or
- Quote the variables, so even an empty or undefined one will be seen as an empty string. Although at this point you can only use string, not numerical comparison.
if [ "$a" != "$b" ]
- 确保在此类测试之前设置变量，或
- 引用变量，因此即使是空的或未定义的变量也将被视为空字符串。虽然此时您只能使用字符串，而不是数字比较。
if [ "$a" != "$b" ]
