For people that find that don't have an 'n' option (like me on RedHat) you can use cp -u to only write the file if the source is newer than the existing one (or there isn't an existing one).
[edit] As mentioned in the comments, this will overwrite older files, so isn't exactly what the OP wanted. Use ceving's answer for that.
Alpine linux: Below answer is only for case of single file: in alpine cp -n not working (and false | cp -i ... too) so solution working in my case that I found is:
if [ ! -f env.js ]; then cp env.example.js env.js; fi
In above example if env.js file not exists then we copy env.example.js to env.js.
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取自手册页：
示例：
Taken from the man page:
Example:
考虑使用
rsync。根据评论
rsync -a -v src dst不正确，因为它将更新现有文件。Consider using
rsync.As per comments
rsync -a -v src dstis not correct because it will update existing files.就是你想要的。请参阅手册页。
Is what you want. See the man page.
这适用于 RedHat：
更新和不覆盖是不同的。
This will work on RedHat:
Updating and not overwriting is something different.
对于那些发现没有“n”选项的人（比如我在 RedHat 上），您可以使用 cp -u 仅在源比现有源更新时才写入文件（或者有不是现有的）。
[编辑] 正如评论中提到的，这将覆盖旧文件，所以这并不完全是OP想要的。使用 ceving 的答案。
For people that find that don't have an 'n' option (like me on RedHat) you can use
cp -uto only write the file if the source is newer than the existing one (or there isn't an existing one).[edit] As mentioned in the comments, this will overwrite older files, so isn't exactly what the OP wanted. Use ceving's answer for that.
Alpine linux：以下答案仅适用于单个文件的情况：在 alpine 中
cp -n不起作用（并且false | cp -i ...也是）所以我发现在我的情况下工作的解决方案是：在上面的示例中，如果
env.js文件不存在，那么我们将env.example.js复制到env.js。Alpine linux: Below answer is only for case of single file: in alpine
cp -nnot working (andfalse | cp -i ...too) so solution working in my case that I found is:In above example if
env.jsfile not exists then we copyenv.example.jstoenv.js.某些版本的 cp 没有 --no-clobber 选项。在这种情况下：
Some version of cp do not have the --no-clobber option. In that case:
这对我有用
是的| cp -i 源 目标
This works for me
yes n | cp -i src dest