Īt some point, as Snake was about to leave on a mission, DD managed to obey a stay command from Ocelot, indicating that he had learned discipline, although DD then ran to Snake before Ocelot could command him to do so, and then Ocelot ordered him to jump up into the UTH-66 Blackfoot chopper. Snake agreed, noting the irony of an ocelot raising hounds. Believing that the pup may be useful in the future, Ocelot intended to train him, comparing him to a diamond in the rough that required some polishing. Ocelot explained that the puppy had been a troublemaker after it had arrived, and that he was unsure of its specific breed. The puppy was present with Ocelot upon Snake's return to Mother Base, licking the latter's face as he picked him up. DD was later taken by Fulton Recovery to Diamond Dogs' Mother Base, his new home. The puppy was found alone by Venom Snake during a mission in 1984. So it likely won't give you any information for copying between /dev/zero and /dev/null, but it might work in your real use case.Biography Phantom Pain Incident See also: Hospital Escape and Phantom Pain IncidentĪs a puppy, DD lost his right eye and was presumably an orphan.
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I don't know if it's updated for block devices. However, note that the file descriptor position may not updated with special files such as /dev/zero, /dev/null, pipes or sockets. $ cp /dev/zero /dev/null & pid=$!Īnd you can check the position on the file descriptor $n$ in /proc/$pid/fd/$n. You can check which file is open on which file descriptor through the symbolic links in /proc/$pid/fd. BusyBox cp typically reads from fd 3 and writes to fd 4. Find out the process ID $pid that's doing the copy, and which file descriptors it's using for input and output. It doesn't depend on what program is doing the copy, though it doesn't always work with special files. On Linux, there is a generic way to know the point that a copy has reached. Why would there be another way which would be harder to implement? There's already a simple, historically established, standard, easy way to do it. If its possible to get dd to print its current status without sending any signal to the process The main cost is kernel time for the benchmarking program, not dd, so it's intrinsic in what you want to do, not in the way you implement it. No, you have your orders of magnitude wrong. So this doesn't invalidate your benchmark in any way. However the pause is only a few CPU instructions (the most costly part by far is printing the progress output).
![watch dev dd s01e04 watch dev dd s01e04](https://static.episodate.com/images/episode/66784-513.jpg)
Technically yes, it has to “pause” to handle the signal. Is it true that 'dd' "pauses" every time it receives an USR1 signal?
![watch dev dd s01e04 watch dev dd s01e04](https://jiocinemaweb.cdn.jio.com/jioimages.cdn.jio.com/content/entry/dynamiccontent/thumbs/550/-/0/8/2/c74fbad0b68b11e786edd767f5890481_1508661011920_l_medium.jpg)
So with BusyBox ≥1.23, cat and cp are very likely to be faster than dd. Only plain copies such as cat and cp use sendfile, however: dd is forced to use read/ write because it wants precise control over the sizes. Note that since version 1.23, BusyBox uses the sendfile system call to copy data, instead of using read and write. And its performance advantage is small at best if you hand-pick an optimal block size for your particular system configuration: cat or cp can do better, and at most is only slightly slower. Note that dd can mangle data, at least when using the bs parameter. What I'm referring to is: # bs with 1Mib so I can have more control on the test.ĭd if=/dev/zero of=/dev/null bs=1048576 count=1024
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Second question: Assuming yes as an answer to the first question, I would like to know if it's possible to get dd to print its current status without sending any signal to the process, maybe some kind of redirection for STDOUT (like 2>&1)? If dd pauses every second then I'll be adding hours to the operation when tens of gigabytes are being transferred. I want to get an output of the current operation every second because the data that's passing through dd is fluctuating and it is important to me to recognize when the transfer rate drops.įirst question: Is it true that 'dd' "pauses" every time it receives a USR1 signal? I'm trying to do some benchmark tests with dd so I would like to have minimal impact on the dd operation. It says that by sending the USR1 signal to dd it "pauses" the process and dd after printing its current status will continue with the job it was doing. I'm on a Linux busybox 1.27 only system so no output=progress available, no busybox's own implementation of pv which is pipe_progress nor pv itself.