麻烦管道通过的sed [英] Trouble with piping through sed

问题描述

我有麻烦的管道通过sed的。一旦我的管道输出到SED，我不能管其他的sed，输出

I am having trouble piping through sed. Once I have piped output to sed, I cannot pipe the output of sed elsewhere.

wget -r -nv http://127.0.0.1:3000/test.html

输出：

2010-03-12 04:41:48 URL:http://127.0.0.1:3000/test.html [99/99] -> "127.0.0.1:3000/test.html" [1]
2010-03-12 04:41:48 URL:http://127.0.0.1:3000/robots.txt [83/83] -> "127.0.0.1:3000/robots.txt" [1]
2010-03-12 04:41:48 URL:http://127.0.0.1:3000/shop [22818/22818] -> "127.0.0.1:3000/shop.29" [1]

我管通过sed的输出来获得URL的清洁列表：

I pipe the output through sed to get a clean list of URLs:

wget -r -nv http://127.0.0.1:3000/test.html 2>&1 | grep --line-buffered -v ERROR | sed 's/^.*URL:\([^ ]*\).*/\1/g'

输出：

http://127.0.0.1:3000/test.html
http://127.0.0.1:3000/robots.txt
http://127.0.0.1:3000/shop

我想那么转储输出到文件，所以我这样做：

I would like to then dump the output to file, so I do this:

wget -r -nv http://127.0.0.1:3000/test.html 2>&1 | grep --line-buffered -v ERROR | sed 's/^.*URL:\([^ ]*\).*/\1/g' > /tmp/DUMP_FILE

我打断这个过程几秒钟后，并检查文件，但它是空的。

I interrupt the process after a few seconds and check the file, yet it is empty.

有趣，下面的产率没有输出（与上述相同，但通过猫管道SED输出）：

Interesting, the following yields no output (same as above, but piping sed output through cat):

wget -r -nv http://127.0.0.1:3000/test.html 2>&1 | grep --line-buffered -v ERROR | sed 's/^.*URL:\([^ ]*\).*/\1/g' | cat

我为什么不能管的sed像猫另一个程序的输出？

Why can I not pipe the output of sed to another program like cat?

推荐答案

在sed的正在写另一个进程或文件，就会缓存数据。

When sed is writing to another process or to a file, it will buffer data.

尝试添加 - 无缓冲选项的sed

Try adding the --unbuffered options to sed.

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