# [BUG?] "git submodule foreach" when command is ssh 5 messages from 2011-01-05 to 2011-01-05. Participants: Chris Packham, Jeff King, Seth Robertson. Thread: https://gitlist.dev/t/26207 ## Chris Packham, 2011-01-05 22:32 Subject: [BUG?] "git submodule foreach" when command is ssh Message-ID: URL: https://gitlist.dev/e/AANLkTi%3Dx2i6NvDNRzbszhk-a-z5AYe46-iUBxQsxJJHC%40mail.gmail.com ``` Hi All, I just noticed something odd with "git submodule foreach". I was running a script to create a backup of each submodule on a server I have ssh access to. I was surprised to find that git submodule foreach stopped silently after the first submodule. A little debugging and I find that git submodule foreach 'ssh localhost "ls /"' - stops silently after the first module (note that the command does produce the expected listing and there is no error about the command failing). git submodule foreach 'echo foo' - works as expected Any thoughts as to whats going on? --- git version 1.7.3.2 ``` ## Chris Packham, 2011-01-05 22:50 Subject: Re: [BUG?] "git submodule foreach" when command is ssh Message-ID: URL: https://gitlist.dev/e/AANLkTini%3DGaGSHDX4e1jhPVxKaSayUJoWa%3Dw4u4Rz-%2B5%40mail.gmail.com In-Reply-To: ``` On Thu, Jan 6, 2011 at 11:32 AM, Chris Packham wrote: > Hi All, > > I just noticed something odd with "git submodule foreach". I was > running a script to create a backup of each submodule on a server I > have ssh access to. I was surprised to find that git submodule foreach > stopped silently after the first submodule. > > A little debugging and I find that > > git submodule foreach 'ssh localhost "ls /"' - stops silently after > the first module (note that the command does produce the expected > listing and there is no error about the command failing). > > git submodule foreach 'echo foo' - works as expected > > Any thoughts as to whats going on? > > --- > git version 1.7.3.2 > 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 ``` ## Seth Robertson, 2011-01-05 23:02 Subject: Re: [BUG?] "git submodule foreach" when command is ssh Message-ID: <201101052302.p05N2E0v002551@no.baka.org> URL: https://gitlist.dev/e/201101052302.p05N2E0v002551%40no.baka.org In-Reply-To: ``` In message , Chri s Packham writes: I just noticed something odd with "git submodule foreach". I was running a script to create a backup of each submodule on a server I have ssh access to. I was surprised to find that git submodule foreach stopped silently after the first submodule. A little debugging and I find that git submodule foreach 'ssh localhost "ls /"' - stops silently after Putting some input redirection will work around the problem. Presumably some pipe input is going into the ssh accidentally. git submodule foreach 'ssh localhost "ls /" < /dev/null' I'll also just take this moment to advertise gitslave (http://gitslave.sf.net) as an alternate to submodules which may help (or hinder) you--depending on your workflow. It doesn't suffer from this particular problem in any case. -Seth Robertson ``` ## Jeff King, 2011-01-05 23:03 Subject: Re: [BUG?] "git submodule foreach" when command is ssh Message-ID: <20110105230334.GB9774@sigill.intra.peff.net> URL: https://gitlist.dev/e/20110105230334.GB9774%40sigill.intra.peff.net In-Reply-To: ``` On Thu, Jan 06, 2011 at 11:50:58AM +1300, Chris Packham wrote: > 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 ``` ## Chris Packham, 2011-01-05 23:22 Subject: Re: [BUG?] "git submodule foreach" when command is ssh Message-ID: URL: https://gitlist.dev/e/AANLkTikCUKbHUrvXjWVyzmrZMzUtgrLrCDr8wSeFVgsZ%40mail.gmail.com In-Reply-To: <20110105230334.GB9774@sigill.intra.peff.net> ``` On Thu, Jan 6, 2011 at 12:03 PM, Jeff King wrote: > On Thu, Jan 06, 2011 at 11:50:58AM +1300, Chris Packham wrote: > >> 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 Thanks that makes sense and adding -n to my ssh invocations solves the problem. ```