bash 检查文件名是否存在包含空格的文件
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Check if a file exists with a filename containing spaces
提问by casperl
I am testing in Bash for if a file is existing, where the file name is escaped using $(printf '%q' "$FNAME").
我正在 Bash 中测试文件是否存在，其中文件名使用$(printf '%q' "$FNAME").
This always produces an error using if [ -f $FNAME ]as in the commented example below. How can I test for a filename that contains spaces and other characters?
这总是会产生错误if [ -f $FNAME ]，如下面的注释示例所示。如何测试包含空格和其他字符的文件名？
#!/usr/bin/env bash
# code used in Raspberry Pi Podcasting Jukebox project
# youtube-dl -f 17 --get-filename https://www.youtube.com/watch?v=AgkM5g_Ob-w
# returns "HOW ABUNDANCE WILL CHANGE THE WORLD - Elon Musk 2017-AgkM5g_Ob-w.3gp"
# Purpose: To test if file exists before downloading
# for testing purposes using an existing regular file "abc def ghi"
AFILE="abc def ghi"
TFILE=$(printf '%q' "$AFILE") # Escaping filename using printf
echo $TFILE # returns abc\ def\ ghi
# if [ -f $AFILE ] # this test returns false every time with error [:too many arguments
if [ -f $TFILE ] # This test also returns FALSE with err [: too many arguments
then
echo "Existing"
# don't download
else
echo "Not existing"
# youtube-dl http://www.youtube.com/watch?v=AgkM5g_Ob-w
fi
回答by Inian
Always quote your file-name, the idea of using %qfor escaping the spaces is right, but when used with the [operator the unquoted $TFILEis split into multiple words causing the -foperand to receive too many arguments when it was actually expecting a single argument. So once you double-quote it, the white-spaces are preserved and a literal single argument is passed in the conditional.
始终引用您的文件名，%q用于转义空格的想法是正确的，但是当与[运算符一起使用时，未引用$TFILE的被拆分为多个单词，导致-f操作数在实际需要单个参数时接收太多参数。所以一旦你用双引号引用它，空格就会被保留，并且在条件中传递一个文字单个参数。
testFile="abc def ghi"
printf -v quotedFile '%q' "$testFile"
if [ -f "$quotedFile" ]; then
printf 'My quoted file %s exists\n' "$quotedFile"
fi
the above should apply well (the usage of [) in any POSIX compatible shells. But if you are targeting scripts for bashshell alone, you can use the [[in which quoting is never necessary as it evaluated as an expression. So you can just do
以上应该适用[于任何 POSIX 兼容的 shell （使用）。但是，如果您仅针对bashshell定位脚本，则可以使用[[其中的引用，因为它被视为表达式。所以你可以做
file_with_spaces="abc def ghi"
if [[ -f $file_with_spaces ]]; then
printf 'My quoted file %s exists\n' "$file_with_spaces"
fi
But in general it doesn't hurt to add quotes to variables in bash. You can always do it.
但总的来说，在bash. 你总是可以做到的。
