bash Shell Script 检查文件是否存在，并具有读取权限
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Shell Script check if file exists, and has read permissions
提问by Asaf Nevo
In my shell script i'm trying to check if a specific file is exists and if it has reading permissions.
在我的 shell 脚本中，我试图检查特定文件是否存在以及它是否具有读取权限。
My file's path has spaces in it.
我的文件路径中有空格。
I quoted the file path:
我引用了文件路径：
file='/my/path/with\ some\ \spaces/file.txt'
This is the function to check if the file exists:
这是检查文件是否存在的函数：
#Check if file exists and is readable
checkIfFileExists() {
#Check if file exists
if ! [ -e ]; then
error " does not exists";
fi
#Check if file permissions allow reading
if ! [ -r ]; then
error " does not allow reading, please set the file permissions";
fi
}
Here I double quote to make sure it gets the file as a one argument:
在这里我用双引号来确保它将文件作为一个参数：
checkIfFileExists "'$file'";
And I receive an error from the bash saying:
我从 bash 收到一条错误消息：
[: too many arguments
Which make me thinks it doesn't get it as a one argument.
这让我认为它不能作为一个论点。
But in my custom error, I do get the whole path, and it says it doesn't exists.
但是在我的自定义错误中，我确实得到了整个路径，并且它说它不存在。
Error: '/my/path/with\ some\ \spaces/file.txt' does not exists
Although it does exists, and when I tried to read it with "cat $file" I get a permission error..
虽然它确实存在，但当我尝试用“cat $file”读取它时，我收到了一个权限错误..
what am I'm doing wrong?
我做错了什么？
采纳答案by tripleee
The proper way to quote when you require variable interpolation is with double quotes:
当您需要变量插值时，正确的引用方法是使用双引号：
if [ -e "" ]; then
You need similar quoting throughout the script, and the caller needs to quote or escape the string -- but not both. When you assign it, use one of these:
您需要在整个脚本中使用类似的引用，并且调用者需要引用或转义字符串——但不能同时引用或转义字符串。当您分配它时，请使用以下之一：
file='/my/path/with some spaces/file.txt'
# or
file=/my/path/with\ some\ spaces/file.txt
# or
file="/my/path/with some spaces/file.txt"
then use double quotes around the value to pass it in as a single argument:
然后在值周围使用双引号将其作为单个参数传入：
checkIfFileExists "$file"
Again, where you need the variable's value to be interpolated, use double quotes.
同样，在需要插入变量值的地方，请使用双引号。
For a quick illustration of what these quotes do, try this:
要快速说明这些报价的作用，请尝试以下操作：
vnix$ printf '<<%s>>\n' "foo bar" "'baz quux'" '"ick poo"' \"ick poo\" ick\ poo
<<foo bar>>
<<'baz quux'>>
<<"ick poo">>
<<"ick>>
<<poo">>
<<ick poo>>
Furthermore, see also When to wrap quotes around a shell variable?
此外，另请参阅何时将引号括在 shell 变量周围？
回答by Vishnu
if [[ -e ]];then
echo it exists
else
echo it doesnt
fi
if [[ -r ]];then
echo readable
else
echo not readable
fi
