Re: [BUG?] "git submodule foreach" when command is ssh

From: Jeff King <peff@peff.net>
Date: Jan 5, 2011, 23:03 UTC
Message-ID: <20110105230334.GB9774@sigill.intra.peff.net>
In-Reply-To: <AANLkTini=GaGSHDX4e1jhPVxKaSayUJoWa=w4u4Rz-+5@mail.gmail.com>

On Thu, Jan 06, 2011 at 11:50:58AM +1300, Chris Packham wrote:

Show 10 quoted lines

> Actually this might be a ssh/bash bug (feature?). There is different
> behaviour between
> 
>   find . -maxdepth 1 -type d -a ! -name '\.*' | while read; do echo
> $REPLY && ssh localhost ls /; done
> 
> and
> 
>   find . -maxdepth 1 -type d -a ! -name '\.*' | while read; do echo
> $REPLY && ls /; done

Ssh will opportunistically eat data on stdin to send to the other side, even though the command on the other side ("ls" in this case) will never read it. Because of course ssh has no way of knowing that, and is trying to be an interactive terminal. So it ends up eating some random amount of the data you expected to go to the "read" call.

You can use the "-n" option to suppress it. For example:

  $ (echo foo; echo bar) |
    while read line; do
      echo local $line
      ssh host "echo remote $line"
    done

produces:

  local foo
  remote foo

but:

  $ (echo foo; echo bar) |
    while read line; do
      echo local $line
      ssh -n host "echo remote $line"
    done

produces:

  local foo
  remote foo
  local bar
  remote bar

which is what you want.

-Peff