`if [-e file.txt]` 在 bash 中不起作用
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`if [-e file.txt]` not working in bash
提问by Eddy
I'm trying to check if a file exists using bash. This is my code
我正在尝试使用 bash 检查文件是否存在。这是我的代码
if [-e file.txt]; then
echo "file exists"
else
echo "file doesn't exist"
fi
But when I run it I get:
但是当我运行它时，我得到：
./test.sh: line 3: [-e: command not found
What am I doing wrong?
我究竟做错了什么？
回答by ruakh
[is not a special token in Bash; it's just that the word[is a builtin command (just like echo). So you need a space after it. And, similarly, you need a space before ]:
[不是 Bash 中的特殊标记；只是这个词[是一个内置命令（就像echo）。所以你需要一个空格。而且，类似地，您在 之前需要一个空格]：
if [ -e file.txt ] ; then
That said, I recommend [[ ]]instead — it's safer in a few ways (though it still requires the spaces):
也就是说，我建议[[ ]]改为 - 它在某些方面更安全（尽管它仍然需要空格）：
if [[ -e file.txt ]] ; then
回答by jacekmigacz
if [ -e file.txt ]; then
You need spaces. [and ]are regular programs.
你需要空格。 [和]是常规程序。
回答by Eddy
Woops, turns out I needed a space between [and -e. Like this:
糟糕，原来我需要在[和之间留一个空格-e。像这样：
if [ -e file.txt ]; then
echo "file exists"
else
echo "file doesn't exist"
fi
回答by shellter
the '[' and ']' needs to be 'on--their-own', i.e. surrounded by spaces.
'[' 和 ']' 需要是 'on--they-own'，即被空格包围。
if [ -e file.txt ] *emphasized text*; then
echo "file exists"
else
echo "file doesn't exist"
fi
