touch-packages team mailing list archive

[Michael Kerrin <michael.kerrin@xxxxxx>]

Public bug reported:

The following bash script will fail randomly on trusty but when tested
on saucy it worked all the time. On the system we test we have kvm
installed and the if statement should evaluate to false and we should
see ten PASS lines and no Error. And this should happen all the time.

======
#!/bin/bash 

set -eu
set -o pipefail

if ! lsmod | grep -q -e ^kvm_intel -e ^kvm_amd ; then
    echo 'Error: check that virtualisation is enabled in your BIOS'
else
    echo "PASS"
fi
=======

As can be seen if I run it 10 times I get 2 PASS and 8 failures

=======
kerrin@kerrin-HP-Z620-Workstation:~/ce_build$ for i in $(seq 0 9) ; do bash test-simple.bash ; done
PASS
PASS
Error: check that virtualisation is enabled in your BIOS
Error: check that virtualisation is enabled in your BIOS
Error: check that virtualisation is enabled in your BIOS
Error: check that virtualisation is enabled in your BIOS
Error: check that virtualisation is enabled in your BIOS
Error: check that virtualisation is enabled in your BIOS
Error: check that virtualisation is enabled in your BIOS
Error: check that virtualisation is enabled in your BIOS
=======

Now if I turn off the pipefail then the script passes all the time and
just prints out 10 PASS lines.

The script uses bash, grep and lsmod and I have the following versions
on trusty of them

kerrin@kerrin-HP-Z620-Workstation:~/ce_build$ dpkg -l | grep bash
ii  bash                                                  4.3-7ubuntu1.5                                      amd64        GNU Bourne Again SHell
ii  bash-completion                                       1:2.1-4                                             all          programmable completion for the bash shell
ii  command-not-found                                     0.3ubuntu12                                         all          Suggest installation of packages in interactive bash sessions
kerrin@kerrin-HP-Z620-Workstation:~/ce_build$ dpkg -l | grep grep
ii  grep                                                  2.16-1                                              amd64        GNU grep, egrep and fgrep
kerrin@kerrin-HP-Z620-Workstation:~/ce_build$ dpkg -l | grep kmod
ii  kmod                                                  15-0ubuntu6                                         amd64        tools for managing Linux kernel modules
ii  libkmod2:amd64                                        15-0ubuntu6                                         amd64        libkmod shared library
ii  module-init-tools                                     15-0ubuntu6                                         all          transitional dummy package (module-init-tools to kmod)

** Affects: bash (Ubuntu)
     Importance: Undecided
         Status: Confirmed

-- 
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https://bugs.launchpad.net/bugs/1394136

Title:
  if statement with pipe to grep randomly fails if pipefail is set

Status in “bash” package in Ubuntu:
  Confirmed

Bug description:
  The following bash script will fail randomly on trusty but when tested
  on saucy it worked all the time. On the system we test we have kvm
  installed and the if statement should evaluate to false and we should
  see ten PASS lines and no Error. And this should happen all the time.

  ======
  #!/bin/bash 

  set -eu
  set -o pipefail

  if ! lsmod | grep -q -e ^kvm_intel -e ^kvm_amd ; then
      echo 'Error: check that virtualisation is enabled in your BIOS'
  else
      echo "PASS"
  fi
  =======

  As can be seen if I run it 10 times I get 2 PASS and 8 failures

  =======
  kerrin@kerrin-HP-Z620-Workstation:~/ce_build$ for i in $(seq 0 9) ; do bash test-simple.bash ; done
  PASS
  PASS
  Error: check that virtualisation is enabled in your BIOS
  Error: check that virtualisation is enabled in your BIOS
  Error: check that virtualisation is enabled in your BIOS
  Error: check that virtualisation is enabled in your BIOS
  Error: check that virtualisation is enabled in your BIOS
  Error: check that virtualisation is enabled in your BIOS
  Error: check that virtualisation is enabled in your BIOS
  Error: check that virtualisation is enabled in your BIOS
  =======

  Now if I turn off the pipefail then the script passes all the time and
  just prints out 10 PASS lines.

  The script uses bash, grep and lsmod and I have the following versions
  on trusty of them

  kerrin@kerrin-HP-Z620-Workstation:~/ce_build$ dpkg -l | grep bash
  ii  bash                                                  4.3-7ubuntu1.5                                      amd64        GNU Bourne Again SHell
  ii  bash-completion                                       1:2.1-4                                             all          programmable completion for the bash shell
  ii  command-not-found                                     0.3ubuntu12                                         all          Suggest installation of packages in interactive bash sessions
  kerrin@kerrin-HP-Z620-Workstation:~/ce_build$ dpkg -l | grep grep
  ii  grep                                                  2.16-1                                              amd64        GNU grep, egrep and fgrep
  kerrin@kerrin-HP-Z620-Workstation:~/ce_build$ dpkg -l | grep kmod
  ii  kmod                                                  15-0ubuntu6                                         amd64        tools for managing Linux kernel modules
  ii  libkmod2:amd64                                        15-0ubuntu6                                         amd64        libkmod shared library
  ii  module-init-tools                                     15-0ubuntu6                                         all          transitional dummy package (module-init-tools to kmod)

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