Hardy Release Notes should note upgrade to Bash 3.2 changes regex syntax

[Robert]

Binary package hint: bash

The following regular expression should work in bash (and used to work in Edgy), but no longer does:

  if [[ "foo.tex" =~ '^(.*)\.tex$' ]]
  then
    file=${BASH_REMATCH[1]}
    echo "File is: $file"
  else
    echo "Not a TeX file"
  fi

It appears that regular expressions using the dot, star, carat and dollar-sign metacharacters no longer work.

[Johnathon (kirrus)]

The feisty move upgraded bash from Bash 3.1 to 3.2. Would this have had an effect on your script? (i.e. has the regex stuff been changed in the newer bash?)

[Robert (robrwo)]

Well, it looks like that did affect it, according to a
  http://en.wikipedia.org/wiki/Bash#In-process_regular_expressions

Basically, the single quotes surrounding the regex become part of the regex. So the above code becomes:

  if [[ "foo.tex" =~ ^(.*)\.tex$ ]]
    then
      file=${BASH_REMATCH[1]}
      echo "File is: $file"
    else
      echo "Not a TeX file"
  fi

That's a pretty significant change. A lot of scripts will be broken. More warning should have been given to users about this.

[Robert (robrwo)]

The release notes at http://www.ubuntu.com/getubuntu/releasenotes/704 do not mention anything about an upgrade to Bash 3.2. They should be amended to note this.

[Johnathon (kirrus)]

Confirming

[Johnathon (kirrus)]

Not needed on the bash lists, site issue only.

[Robert (robrwo)]

I do wonder if a version of Bash 3.1 should be included as an option in the distro. The change was unexpected and enough to hurt me at least one script that I wrote, and may be the cause of problems I've hard with an install script from a third party which kept insisting that I did not have prereqs installed which I did (it was paring the output of --version calls).

I suspect this is affecting a few people who run Ubuntu server. There should at least be an option for them to downgrade to an earlier version of bash to lessen the burden.

[Johnathon (kirrus)]

I would recommend adding a new bug. Mail me the number, and I'll confirm
it, we have been affected by a problem with the bash upgrade as well.
(Firehol is not able to work with bash 3.2. There is a sneaky
workaround, but it's not good.)

[Robert (robrwo)]

I've just added Bug #110407

[Robert (robrwo)]

This needs to be documented for the LTS release of Hardy. If Bus #110407 is acted on, then users will have an alternative.

[Jamie (ubuntu-websites)]

This should not have been assigned to me. I am not part of the programming project. It should be assigned to someone else.

[Jamie (ubuntu-websites)]

This shouldn't have been assigned to me. I am not related to this project.

[Robert (robrwo)]

Is someone going to act on this? It shouldn't be too difficult to add a note to the website and release notes warning users about potential problems.

[Johnathon (kirrus)]

try emailing <email address hidden>, and point them at this bug.

[Johnathon (kirrus)]

Not a problem anymore - bashrc patched.