Feature Request (with PR): just run axel if state file is not possible (when writing real file to /dev/null)

[sanderjo]

I want to use axel to measure my Internet speed, with a file meant for that (https://speed.hetzner.de/100MB.bin). I do not want to measure my disk speed, so I try to write to /dev/null:

$ axel  https://speed.hetzner.de/100MB.bin -o /dev/null 
Initializing download: https://speed.hetzner.de/100MB.bin
File size: 104857600 bytes
No state file, cannot resume!

Probably axel wants to write to and read from /dev/null/100MB.bin.st, which does not work.

Proposal: if no state file can written/read, just say so, and do the download anyway.

Example of the impact of the disk speed on the measurement:

axel  https://speed.hetzner.de/100MB.bin -o .
Downloaded 100 Megabyte(s) in 1 second(s). (59295,84 KB/s)

axel  https://speed.hetzner.de/100MB.bin -o /media/zeegat/
Downloaded 100 Megabyte(s) in 4 second(s). (24952,65 KB/s)

Much lower "Internet" speed, due to the lower disk speed (as limiting factor).

Result: I can't determine my Internet speed. Mabye it's 8 Gbps so about 900 MB/s, but my disks are the limiting factor.

[sanderjo]

I got it working: "writing" the to-be-downloaded file to /dev/null is now possible, and thus measuring pure Internet speed (no limiting disk speed).

Note the text No state file, cannot resume! Running anyway ...

sander@zwart2204:~/Downloads/axel-2.17.11$ ./axel  http://speed.hetzner.de/100MB.bin -o /dev/null 
Initializing download: http://speed.hetzner.de/100MB.bin
File size: 100 Megabyte(s) (104857600 bytes)
No state file, cannot resume! Running anyway ...
Opening output file /dev/null
Starting download

Connection 0 finished
Connection 2 finished
Connection 1 finished
Connection 3 finished
Connection 0 finished
Connection 2 finished
Connection 1 finished
Connection 3 finished
Connection 0 finished
Connection 2 finished
Connection 3 finished
[100%] [........................................................................................................................................] [  21,9MB/s] [00:00]

Downloaded 100 Megabyte(s) in 4 second(s). (22402,76 KB/s)

[NuxRo]

Excellent, I was really struggling to find a good parallel downloader that doesn't benchmark the disk.
Looking forward to next release.