"heroku run" sends "attached to terminal" message to stdout

[brandon-rhodes]

The "heroku run" command fouls the output of the command that it is running by putting its own status message on standard out, instead of on standard error where it belongs:

$ heroku run echo hi | wc
  2       9      55

Of course, "echo hi" should produce one line of output, not two—which would be the case if the following message were sent to standard error:

Running `echo hi` attached to terminal... up, run.1

This error makes it difficult to pass the output of "heroku run" into other Unix programs, like "grep" or "sort"—one has to write commands like:

$ heroku run find myapp/lib/ | (read throwaway; grep py)

Compare with the behavior of "ssh", which always sends status information to stderr:

$ ssh another_host echo hi | wc
...
... logging output ...
...
      1       1       3

[wuputah]

I think there was some intent for this under #256; stdout should not be modified if the output channel is not a tty.

You can work around this by doing:

$ heroku run echo hi | tail -n +2

[duffytilleman]

+1 on this. #256 and #811 only addressed piping stdin. Heroku run is still writing to stdout, which is frustratingly bad practice. See for instance http://www.gnu.org/software/libc/manual/html_node/Standard-Streams.html or http://en.wikipedia.org/wiki/Standard_streams