bash 如何在一个命令中卷曲多个资源？
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How do I curl multiple resources in one command?
提问by Coder
Say I am trying to download a set of 50 lecture notes efficiently. These notes are inside the profsubdirectory of a university website. The 45th lecture note is inside the lect45subdirectory as a pdf entitled lect45.pdf. I get my first pdf as follows:
假设我正在尝试有效地下载一组 50 个讲义。这些笔记prof位于大学网站的子目录中。第 45 个讲义位于lect45子目录中，名为 .pdf 的 pdf 文件lect45.pdf。我得到我的第一个 pdf 如下：
curl -O http://www.university.edu/~prof/lect1/lect1.pdf
How do I get all my 50 notes efficiently using cURL and bash? I'm trying to do this from the command line, not through a Python / Ruby / Perl script. I know something like the below will generate a lot of 404s:
如何使用 cURL 和 bash 有效地获取所有 50 个笔记？我正在尝试从命令行执行此操作，而不是通过 Python/Ruby/Perl 脚本。我知道类似下面的内容会产生很多 404：
curl -O http://www.university.edu/~prof/lect{1..50}/lect{1..50}.pdf
so what will work better? I would prefer an elegant one-liner over a loop.
那么什么会更好呢？我更喜欢优雅的单线而不是循环。
回答by Alfe
Do it in several processes:
分几个过程做：
for i in {1..50}
do
curl -O http://www.university.edu/~prof/lect$i/lect$i.pdf &
done
or as a one-liner (just a different formatting):
或作为单行（只是不同的格式）：
for i in {1..50}; do curl -O http://www.university.edu/~prof/lect$i/lect$i.pdf & done
The &makes all processes run in parallel.
这&使得所有进程并行运行。
Don't be scared by the output; the shell tells you that 50 processes have been started, that's a lot of spam. Later it will tell you for each of these that they terminated. A lot of output again.
不要被输出吓到；shell 告诉您已经启动了 50 个进程，这是很多垃圾邮件。稍后它会告诉你他们终止的每一个。再次大量输出。
You probably don't want to run all 50 in parallel ;-)
您可能不想并行运行所有 50 个 ;-)
EDIT:
编辑：
Your example using {1..50}twice makes a matrix of the numbers. See for example echo {1..3}/{1..3}to see what I mean. And I guess that this way you create a lot of 404s.
您使用{1..50}两次的示例构成了数字矩阵。例如echo {1..3}/{1..3}，请参阅以了解我的意思。我猜这样你会创建很多 404。
回答by ДМИТРИЙ МАЛИКОВ
Take a look at parallelshell tool.
看看parallelshell工具。
So, for this particular case it will look like
所以，对于这种特殊情况，它看起来像
seq 50 | parallel curl -O http://www.university.edu/~prof/lect{}/lect{}.pdf
As for curl- it doesn't have its own parallel mechanism, and what for it actually should? And your example with shell expansions {1..50}seems valid for me.
至于curl- 它没有自己的并行机制，它实际上应该做什么？你的 shell 扩展示例{1..50}对我来说似乎有效。
