[Bug 1390061] Re: bash-completion tilde expansion every time

[Andy Foster]

Confirmed this problem still exists on 16.04 LTS Server.
After joining machine to AD using Winbind, logins with local accounts are noticeably slower and bash completion can be very laggy.
All these conflicting comments have confused me, is there actually a fix available?

-- 
You received this bug notification because you are a member of Ubuntu
Foundations Bugs, which is subscribed to bash-completion in Ubuntu.
https://bugs.launchpad.net/bugs/1390061

Title:
  bash-completion tilde expansion every time

Status in bash-completion package in Ubuntu:
  Confirmed

Bug description:
  1) The release of Ubuntu you are using, via 'lsb_release -rd' or System -> About Ubuntu
  root at ubuntu1404:~# lsb_release -rd
  Description:    Ubuntu 14.04.1 LTS
  Release:        14.04

  2) The version of the package you are using, via 'apt-cache policy pkgname' or by checking in Software Center
  root at ubuntu1404:~# apt-cache policy bash-completion
  bash-completion:
    Installed: 1:2.1-4
    Candidate: 1:2.1-4
    Version table:
   *** 1:2.1-4 0
          500 http://se.archive.ubuntu.com/ubuntu/ trusty/main i386 Packages
          100 /var/lib/dpkg/status

  3) What you expected to happen

  When I use bash-completion it should not read the /etc/passwd file or contact the Active directory.
  It is very hard to see this problem unless you run this on a machine with slow authentication... but the commands below will show if the /etc/passwd or sssd are used by bash_completion or not:

  root at ubuntu1404:~# strace bash -c ". /etc/bash_completion; quote_readline '/something'; echo" 2>&1 | grep /etc/passwd
  root at ubuntu1404:~# strace bash -c ". /etc/bash_completion; quote_readline '/something'; echo" 2>&1 | grep sss

  When the ~ are escaped on line 545 and 547 in /usr/share/bash-
  completion/bash_completion then bash_completion works as expected.

  4) What happened instead

  Every time you use tab-completion in bash on ubuntu 14.04 it will read
  the /etc/passwd file and if sssd are installed and configured for
  Active Directory authentication it will talk to sssd... and this can
  be slow in some environments.

  root at ubuntu1404:~# strace bash -c ". /etc/bash_completion; quote_readline '/something'; echo" 2>&1 | grep /etc/passwd
  open("/etc/passwd", O_RDONLY|O_CLOEXEC) = 3
  root at ubuntu1404:~# strace bash -c ". /etc/bash_completion; quote_readline '/something'; echo" 2>&1 | grep sss
  open("/lib/i386-linux-gnu/libnss_sss.so.2", O_RDONLY|O_CLOEXEC) = 3
  open("/var/lib/sss/mc/passwd", O_RDONLY|O_LARGEFILE|O_CLOEXEC) = 3
  connect(4, {sa_family=AF_LOCAL, sun_path="/var/lib/sss/pipes/nss"}, 110) = 0

  I have made a small patch for this problem and I have not found any side effects:
  --- /usr/share/bash-completion/bash_completion.orig     2014-11-06 10:36:14.981888369 +0100
  +++ /usr/share/bash-completion/bash_completion  2014-11-06 10:36:25.142070963 +0100
  @@ -542,9 +542,9 @@
       elif [[ $1 == \'* ]]; then
           # Leave out first character
           printf -v $2 %s "${1:1}"
  -    elif [[ $1 == ~* ]]; then
  +    elif [[ $1 == \~* ]]; then
           # avoid escaping first ~
  -        printf -v $2 ~%q "${1:1}"
  +        printf -v $2 \~%q "${1:1}"
       else
           printf -v $2 %q "$1"
       fi

To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/bash-completion/+bug/1390061/+subscriptions