lxc-info output different in terminal and file redirection

[Olivier Clavel]

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Versions information

root@arachide:~# lsb_release -rd
Description: Ubuntu 14.04.1 LTS
Release: 14.04

root@arachide:~# apt-cache policy lxc
lxc:
  Installed: 1.0.6-0ubuntu0.1
  Candidate: 1.0.6-0ubuntu0.1
  Version table:
 *** 1.0.6-0ubuntu0.1 0
        500 http://fr.archive.ubuntu.com/ubuntu/ trusty-updates/main amd64 Packages
        100 /var/lib/dpkg/status
     1.0.3-0ubuntu3 0
        500 http://fr.archive.ubuntu.com/ubuntu/ trusty/main amd64 Packages

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lxc-info output is different when displayed directly in the terminal or redirected to a file

Expected: same content when displayed in term or redirected to a file
Actual result: contents different

This behavior broke a custom script which was working like a charm on Ubuntu 13.10 with lxc version 1.0.0~alpha1 amd64. This is working correctly as well on Ubuntu 14.04 with the stock trusty version of lxc in the main repo (1.0.3)

How to reproduce:

root@arachide:~# lxc-info -n my_lxc
Name: my_lxc
State: STOPPED
root@arachide:~# lxc-info -n my_lxc > test.txt
root@arachide:~# cat test.txt
Name: my_lxc
Name: my_lxc
State: STOPPED
Name: my_lxc
State: STOPPED
Name: my_lxc
State: STOPPED
Name: my_lxc
State: STOPPED
Name: my_lxc
State: STOPPED
Name: my_lxc
State: STOPPED
root@arachide:~#

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Serge Hallyn (serge-hallyn)]

I believe what is happening is that some of the api bindings are forking with un-flushed data in the stdout buffer; then the data gets printed on exit by each thread.

[Stéphane Graber (stgraber)]

Pretty sure we fixed that one a while back (and a similar issue in lxc-autostart too).