Bash：连接多个文件并在每个文件之间添加“\newline”？
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Bash: concatenate multiple files and add "\newline" between each?
提问by pimpampoum
I have a small Bash script that takes all Markdown files of a directory, and merge them into one like this:
我有一个小的 Bash 脚本，它获取一个目录的所有 Markdown 文件，并将它们合并为一个，如下所示：
for f in *.md; do (cat "${f}";) >> output.md; done
It works well. Now I'd like to add the string "\newline" between each document, something like this:
它运作良好。现在我想在每个文档之间添加字符串“\newline”，如下所示：
for f in *.md; do (cat "${f}";) + "\newline" >> output.md; done
How can I do that? The above code obviously doesn't work.
我怎样才能做到这一点？上面的代码显然不起作用。
回答by Tom Fenech
If you want the literal string "\newline", try this:
如果你想要文字 string "\newline"，试试这个：
for f in *.md; do cat "$f"; echo "\newline"; done > output.md
This assumes that output.mddoesn't already exist. If it does (and you want to include its contents in the final output) you could do:
这假设output.md不存在。如果确实如此（并且您想将其内容包含在最终输出中），您可以执行以下操作：
for f in *.md; do cat "$f"; echo "\newline"; done > out && mv out output.md
This prevents the error cat: output.md: input file is output file.
这可以防止错误cat: output.md: input file is output file。
If you want to overwrite it, you should just rmit before you start.
如果你想覆盖它，你应该rm在开始之前。
回答by jaypal singh
You can do:
你可以做：
for f in *.md; do cat "${f}"; echo; done > output.md
You can add an echocommand to add a newline. To improve performance I would recommend to move the write >outside the forloop to prevent reading and writing of file at every iteration.
您可以添加一个echo命令来添加换行符。为了提高性能，我建议将写入移动到循环>之外，for以防止在每次迭代时读取和写入文件。
回答by gniourf_gniourf
Here's a funny possibility, using ed, the standard editor:
这是一个有趣的可能性，使用ed标准编辑器：
ed -s < <(
for f in *.md; do
[[ $f = output.md ]] && continue
printf '%s\n' "r $f" a '\newline' .
done
printf '%s\n' "w output.md" "q"
)
(I've inserted a line to exclude output.mdfrom the inserted files).
（我插入了一行以output.md从插入的文件中排除）。
For each file:
对于每个文件：
r $f:rised's insert filecommand,a:edstarts a newline after the current line for editing,\newline: well, we're insertion mode, soedjust inserts this,.: to stop insert mode.
r $f:rised的插入文件命令，a:ed在当前行之后开始换行以进行编辑，\newline: 好吧，我们是插入模式，所以ed只需插入这个，.: 停止插入模式。
At the end, we write the buffer to the file output.mdand quit.
最后，我们w将缓冲区写入文件output.md和quit。
