[Bug 1054502] Re: man page dd - Sending USR1 signal

[Dave Gilbert]

That example certainly isn't clear.

I don't think you need the kill -CONT,   as far as I can tell the -USR1 will display the info and just carry on without
any other requirement.
So it's not obvious to me what the kill $pid in the original example is supposed to do, if you look at the info page
for dd it uses a more complex example that makes some more sense:

   Sending an `INFO' signal to a running `dd' process makes it print
I/O statistics to standard error and then resume copying.  In the
example below, `dd' is run in the background to copy 10 million blocks.
The `kill' command makes it output intermediate I/O statistics, and
when `dd' completes normally or is killed by the `SIGINT' signal, it
outputs the final statistics.

     $ dd if=/dev/zero of=/dev/null count=10MB & pid=$!
     $ kill -s INFO $pid; wait $pid
     3385223+0 records in
     3385223+0 records out
     1733234176 bytes (1.7 GB) copied, 6.42173 seconds, 270 MB/s
     10000000+0 records in
     10000000+0 records out
     5120000000 bytes (5.1 GB) copied, 18.913 seconds, 271 MB/s

   On systems lacking the `INFO' signal `dd' responds to the `USR1'
signal instead, unless the `POSIXLY_CORRECT' environment variable is
set.

  It's possible the kill $pid in the example is just there to kill off
the backgrounded dd.

Confirming because at the very least the example is confusing.

** Changed in: coreutils (Ubuntu)
   Importance: Undecided => Low

** Changed in: coreutils (Ubuntu)
       Status: New => Confirmed

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https://bugs.launchpad.net/bugs/1054502

Title:
  man page dd - Sending USR1 signal

Status in “coreutils” package in Ubuntu:
  Confirmed

Bug description:
  I read this in the man page dd

         Sending a USR1 signal to a running `dd' process makes it print
  I/O statistics to standard error and then resume copying.

                $ dd if=/dev/zero of=/dev/null& pid=$!
                $ kill -USR1 $pid; sleep 1; kill $pid

                18335302+0 records in 18335302+0 records out 9387674624
  bytes (9.4 GB) copied, 34.6279 seconds, 271 MB/s

  But when I tried 'kill -USR1 $pid; sleep 1; kill $pid', dd didn't
  resume.

  I correct it with

  kill -USR1 $pid; sleep 1; kill -CONT $pid

  I'm not sure it could be concidered as bug but the man page isn't
  correct and it should be corrected

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