如何在 Bash 中检查文件是否为空？
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How to check if a file is empty in Bash?
提问by Mich
I have a file called diff.txt. Want to check if it is empty. Did something like this but couldn't get it working.
我有一个名为 diff.txt 的文件。想检查它是否为空。做了这样的事情，但无法让它工作。
if [ -s diff.txt ]
then
touch empty.txt
rm full.txt
else
touch full.txt
rm emtpy.txt
fi
回答by thb
Misspellings are irritating, aren't they? Check your spelling of empty, but then also try this:
拼写错误很烦人，不是吗？检查你的拼写empty，但也试试这个：
#!/bin/bash -e
if [ -s diff.txt ]
then
rm -f empty.txt
touch full.txt
else
rm -f full.txt
touch empty.txt
fi
I like shell scripting a lot, but one disadvantage of it is that the shell cannot help you when you misspell, whereas a compiler like your C++ compiler can help you.
我非常喜欢 shell 脚本，但它的一个缺点是当你拼错时 shell 不能帮助你，而像你的 C++ 编译器这样的编译器可以帮助你。
Notice incidentally that I have swapped the roles of empty.txtand full.txt, as @Matthias suggests.
顺便说一下，正如@Matthias 所建议的那样，我已经交换了empty.txt和的角色full.txt。
回答by mickey white
[ -s file.name ] || echo "file is empty"
回答by Surya
[[ -s file ]] --> Checks if file has size greater than 0
[[ -s file ]] --> 检查文件的大小是否大于 0
if [[ -s diff.txt ]]; then echo "file has something"; else echo "file is empty"; fi
If needed, this checks all the *.txt files in the current directory; and reports all the empty file:
如果需要，这会检查当前目录中的所有 *.txt 文件；并报告所有空文件：
for file in *.txt; do if [[ ! -s $file ]]; then echo $file; fi; done
回答by geedoubleya
While the other answers are correct, using the "-s"option will also show the file is empty even if the file does not exist.
By adding this additional check "-f"to see if the file exists first, we ensure the result is correct.
虽然其他答案是正确的，但"-s"即使文件不存在，使用该选项也会显示文件为空。
通过添加这个额外的检查"-f"来首先查看文件是否存在，我们确保结果是正确的。
if [ -f diff.txt ]
then
if [ -s diff.txt ]
then
rm -f empty.txt
touch full.txt
else
rm -f full.txt
touch empty.txt
fi
else
echo "File diff.txt does not exist"
fi
回答by smarber
@geedoubleyaanswer is my favorite.
@geedoubleya答案是我最喜欢的。
However, I do prefer this
不过，我更喜欢这个
if [[ -f diff.txt && -s diff.txt ]]
then
rm -f empty.txt
touch full.txt
elif [[ -f diff.txt && ! -s diff.txt ]]
then
rm -f full.txt
touch empty.txt
else
echo "File diff.txt does not exist"
fi
回答by Noam Manos
To check if file is empty or has only white spaces, you can use grep:
要检查文件是否为空或只有空格，您可以使用 grep：
if [[ -z $(grep '[^[:space:]]' $filename) ]] ; then
echo "Empty file"
...
fi
回答by Mike Q
Many of the answers are correct but I feel like they could be more complete / simplistic etc. for example :
许多答案是正确的，但我觉得它们可以更完整/简单等，例如：
Example 1 : Basic if statement
示例 1：基本 if 语句
# BASH4+ example on Linux :
typeset read_file="/tmp/some-file.txt"
if [ ! -s "${read_file}" ] || [ ! -f "${read_file}" ] ;then
echo "Error: file (${read_file}) not found.. "
exit 7
fi
if $read_file is empty or not there stop the show with exit. More than once I have had misread the top answer here to mean the opposite.
如果 $read_file 为空，则退出时停止显示。我不止一次误读了这里的最佳答案，意思是相反的。
Example 2 : As a function
示例 2：作为函数
# -- Check if file is missing /or empty --
# Globals: None
# Arguments: file name
# Returns: Bool
# --
is_file_empty_or_missing() {
[[ ! -f "" || ! -s "" ]] && return 0 || return 1
}
回答by Radek 'Goblin' Pieczonka
[[ -f filename && ! -s filename ]] && echo "filename exists and is empty"
回答by Nabeel Shaikh
Easiest way for checking file is empty or not:
检查文件是否为空的最简单方法：
if [ -s /path-to-file/filename.txt ]
then
echo "File is not empty"
else
echo "File is empty"
fi
You can also write it on single line:
你也可以单行写：
[ -s /path-to-file/filename.txt ] && echo "File is not empty" || echo "File is empty"
回答by SamMorrowDrums
I came here looking for how to delete empty __init__.pyfiles as they are implicit in Python 3.3+ and ended up using:
我来这里是为了寻找如何删除空__init__.py文件，因为它们在 Python 3.3+ 中是隐含的，最终使用：
find -depth '(' -type f -name __init__.py ')' -print0 |
while IFS= read -d '' -r file; do if [[ ! -s $file ]]; then rm $file; fi; done
Also (at least in zsh) using $path as the variable also breaks your $PATH env and so it'll break your open shell. Anyway, thought I'd share!
此外（至少在 zsh 中）使用 $path 作为变量也会破坏您的 $PATH 环境，因此它会破坏您打开的外壳。无论如何，我想我会分享！
