命令未找到重定向输入时出错

Question

我写了一个要在文本文件上运行的shell脚本（称为test.txt）。此脚本将读取输入文件，循环访问其行，并执行一些操作。

我首先编译我的程序：

chmod +x ./cleanLines.txt

然后运行我的命令：

./cleanLines.txt < ./test.txt > output.txt

但是，我得到的错误是：

./cleanLines.txt: line 7: [[: command not found
./cleanLines.txt: line 7: [[#Some: command not found
./cleanLines.txt: line 7: [[HelloWorld: command not found
./cleanLines.txt: line 7: [[Today: command not found
./cleanLines.txt: line 7: [[Cookie: command not found
./cleanLines.txt: line 7: [[: command not found
./cleanLines.txt: line 7: [[Out: command not found
./cleanLines.txt: line 7: [[: command not found
./cleanLines.txt: line 7: [[: command not found

我的测试.txt文件如下：

*blank line*(Won't let me edit it like this here)
#Some note
HelloWorld #note
Today is sunny
Cookie Monster
Out of things to say

和 cleanLines.txt 如下：

#!/bin/bash
    PATH=${PATH[*]}:.
    #filename: clearLines
    while read line; do
        if [[$line != ""]]; then
                .
                .
                # Doing stuff
                .
                .
        fi
    done < test.txt

注意：第 7 行是：

if [[$line != ""]]; then

这里有什么问题？除非我必须这样做，（因为我们被严格告知不要）我宁愿不发布我的其余代码。

Answer 1

空格

很重要。 取代：

if [[$line != ""]]; then

跟：

if [[ $line != "" ]]; then

例子

观察这些失败：

$ line=1 ; [[$line != "" ]] && echo yes
bash: [[1: command not found
$ line=1 ; [[ $line != ""]] && echo yes
bash: conditional binary operator expected
bash: syntax error near `yes'

但是这个版本，具有正确的间距，成功了：

$ line=1 ; [[ $line != "" ]] && echo yes
yes