wget or curl from stdin

问题:

I'd like to download a web pages while supplying URLs from stdin. Essentially one process continuously produces URLs to stdout/file and I want to pipe them to wget or curl. (Think about it as simple web crawler if you want).

This seems to work fine:

tail 1.log | wget -i - -O - -q 

But when I use 'tail -f' and it doesn't work anymore (buffering or wget is waiting for EOF?):

tail -f 1.log | wget -i - -O - -q

Could anybody provide a solution using wget, curl or any other standard Unix tool? Ideally I don't won't want to restart wget in the loop, just keep it running downloading URLs as they come.

回答1:

What you need to use is xargs. E.g.

tail -f 1.log | xargs -n1 wget -O - -q

回答2:

You can do this with cURL, but your input needs to be properly formatted. Example alfa.txt:

url example.com
output example.htm
url stackoverflow.com
output stackoverflow.htm

Alternate example:

url stackoverflow.com/questions
remote-name
url stackoverflow.com/documentation
remote-name

Example command:

cat alfa.txt | curl -K-

回答3:

Use xargs which converts stdin to argument.

tail 1.log | xargs -L 1 wget

回答4:

Try piping the tail -f through python -c $'import pycurl;c=pycurl.Curl()\nwhile True: c.setopt(pycurl.URL,raw_input().strip()),c.perform()'

This gets curl (well, you probably meant the command-line curl and I'm calling it as a library from a Python one-liner, but it's still curl) to fetch each URL immediately, while still taking advantage of keeping the socket to the server open if you're requesting multiple URLs from the same server in sequence. It's not completely robust though: if one of your URLs is duff, the whole command will fail (you might want to make it a proper Python script and add try / except to handle this), and there's also the small detail that it will throw EOFError on EOF (but I'm assuming that's not important if you're using tail -f).