1) Create a temp buffer file
2) Read the file constantly to STDOUT?
3) What does netcat httpbin.org 80 | netcat -lp 8080 do?
What would be a good use of this circular pipeline? Can you give me some example of what you use this for? Thanks
A.)
Some context:
- Our goal here is to match up to two network connections, so that anything we receive on one is forwarded to the other.
- netcat is a "networking swiss army knife", it's a tool for making network connections
- HTTP and bash pipelines both happen to be "line oriented", meaning they operate one line at a time. Exploiting this happy coincedence is what makes this work
- httpbin.org is a metanym for any website you need.
So:
echo "" > /tmp/buffer
tail -f /tmp/buffer
netcat httpbin.org 80
netcat -lp 8080 > /tmp/buffer
B.) I don't think there is one! I've never needed to do this again in the, gosh, seven intervening years. Normally bash pipelines operate like a bucket brigade, moving data unidirectionally through various processing steps, and usually dumping it into a file at the end.
They aren't normally for creating long-lived programs that manage bidirectional flows of data. Which is why writing a web server in bash is a fun challenge.
And I mean this as encouragement, but you should read the synopsis from the GNU netcat manual. It's short and explains it well enough. netcat httpbin.org 80 is using connect mode, the -l one is using listen mode, and -p is --local-port (the port to listen on in listen mode).