[hmpc]

Actually no. From the manpage:

Use "-C -" to tell curl to automatically find out where/how to resume the transfer. It then uses the given output/input files to figure that out.

[foota]

Stupid question, but how do things like this resume from where they left off? Wouldn't the server need to be cooperating in this? Is that build into HTTP?

[laumars]

Yes the server would need to support it. The request is made via a HTTP header (Range[1] IIRC).

Also, I wouldn't consider that a stupid question. :)

[1] https://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#Rang...

[hobarrera]

This is also how download accelerators worked (back in the late nineties, early naught's), by having different connections work at several ranges to maximize bandwidth usage.

[laumars]

Funny enough, it was writing a download accelerator that taught me about the Range HTTP request header.

[zo1]

You specify a byte "range" when requesting a file via HTTP from the server. Not all servers support this, but most do these days.

#Edit. More info here: https://en.wikipedia.org/wiki/Byte_serving

[viperscape]

Just looked that up, that's a rather limited usefulness. The multi homed usage makes sense but feels out of place really.

[joosters]

Why? How could it be more useful? HTTP byte ranges are incredibly flexible, since you one request can specify many byte ranges at once (it's almost too flexible, since a dumb server can easily be overwhelmed by a maliciously complicated request)

It handles the basic case of fetching the remainder of an interrupted download, and can also support partial downloads e.g. for supporting a video stream with the user jumping to different places in the movie.

[raverbashing]

Correct, but very unintuitive

[lmz]

Also doesn't work with the command line utility's retry option as it gets the size only once and does not update it when retrying.