bash 我如何告诉 rsync 仅在目标目录存在时运行？
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How do I tell rsync to run only if the destination directory exists?
提问by Marcus
I have this bash script running my backup to an external hard drive... only if that drive is mounted (OS X):
我有这个 bash 脚本将我的备份运行到外部硬盘驱动器......仅当该驱动器已安装（OS X）：
DIR=/Volumes/External;
if [ -e $DIR ];
then rsync -av ~/dir_to_backup $DIR;
else echo "$DIR does not exist";
fi
This works, but I sense I am misreading the rsync man page. Is there a builtin rsync option to abort the run if the top level destination directory does not exist? Without testing for the existence of /Volumes/External, a directory will be created by that name if it isn't already mounted.
这有效，但我觉得我误读了 rsync 手册页。如果顶级目标目录不存在，是否有内置的 rsync 选项来中止运行？如果不测试 /Volumes/External 的存在，则如果尚未安装目录，则会以该名称创建目录。
回答by Ray Booysen
These two flags look like what you're looking for:
这两个标志看起来像你要找的：
--existing, --ignore-non-existing
From the man page:
从手册页：
--existing, --ignore-non-existing
This tells rsync to skip creating files (including directories) that do not exist yet on the destination. If this option is combined with the --ignore-existing option, no files will be updated (which can be useful if all you want to do is delete extraneous files).
--existing, --ignore-non-existing
这告诉 rsync 跳过创建目标上尚不存在的文件（包括目录）。如果此选项与 --ignore-existing 选项结合使用，则不会更新任何文件（如果您只想删除无关文件，这会很有用）。
回答by mjy
AFAIK no, but you can simulate the behavour with a trailing slash:
AFAIK 不，但您可以使用尾部斜杠模拟行为：
rsync -av dir_to_backup /Volumes/External/;
rsync -av dir_to_backup /Volumes/External/;
It will exit with an error if the directory does not exist (which may or may not be desired).
如果目录不存在（可能需要也可能不需要），它将退出并显示错误。
Also, you can always optimize away the if:
此外，您始终可以优化以下条件：
test -e $DIR && rsync -av ...
test -e $DIR && rsync -av ...
回答by JesperE
No, there does not seem to be any such option, as far as I can see from the manpage.
不，就我从联机帮助页中看到的而言，似乎没有任何此类选项。
