The progress meter is inhibited if curl deems that there is output going to
the terminal, as then would the progress meter interfere with that output and
just mess up what gets displayed. A user can also forcibly switch off the
progress meter with the option, which tells curl to hush.

If you invoke curl and don’t get the progress meter, make sure your output is
directed somewhere other than the terminal.

At times when curl is asked to transfer data, it can’t figure out the total
size of the requested operation and that then subsequently makes the progress
meter contain fewer details and it cannot, for example, make forecasts for
transfer times, etc.

The progress meter displays bytes and bytes per second.

The times are displayed using HSS for hours, minutes and seconds.

Progress meter legend

The progress meter exists to show a user that something actually is
happening. The different fields in the output have the following meaning:

Title	Meaning
%	Percentage completed of the whole transfer
Total	Total size of the whole expected transfer (if known)
%	Percentage completed of the download
Received	Currently downloaded number of bytes
%	Percentage completed of the upload
Xferd	Currently uploaded number of bytes
Average Speed Dload	Average transfer speed of the entire download so far, in number of bytes per second
Average Speed Upload	Average transfer speed of the entire upload so far, in number of bytes per second
Time Total	Expected time to complete the operation, in HHSS notation for hours, minutes and seconds
Time Current	Time passed since the start of the transfer, in HHSS notation for hours, minutes and seconds
Time Left	Expected time left to completion, in HHSS notation for hours, minutes and seconds
Curr.Speed	Average transfer speed over the last 5 seconds (the first 5 seconds of a transfer is based on less time, of course) in number of bytes per second