Matching package version string in /bin/sh - regex

Question

I'm trying to match given string and match it to a package version in a /bin/sh script:
if test "x$version" = "x"; then
version="latest";
info "Version parameter not defined, assuming latest";
else
info "Version parameter defined: $version";
info "Matching version to package version"
case "$version" in
[^4.0.]*)
$package_version='1.0.1'
;;
[^4.1.]*)
$package_version='1.1.1'
;;
[^4.2.]*)
$package_version='1.2.6'
;;
*)
critical "Unable to match requested version to package version"
exit 1
;;
esac
fi
However, when I run it I get an error:
23:38:47 +0000 INFO: Version parameter defined: 4.0.0
23:38:47 +0000 INFO: Matching Puppet version to puppet-agent package version (See http://docs.puppetlabs.com/puppet/latest/reference/about_agent.html for more details)
23:38:47 +0000 CRIT: Unable to match requested puppet version to puppet-agent version - Check http://docs.puppetlabs.com/puppet/latest/reference/about_agent.html
23:38:47 +0000 CRIT: Please file a bug report at https://github.com/petems/puppet-install-shell/
23:38:47 +0000 CRIT:
23:38:47 +0000 CRIT: Version: 4.0.0
I'm using the same regex that worked for me in another part of the script:, and it seems to work there:
if test "$version" = 'latest'; then
apt-get install -y puppet-common puppet
else
case "$version" in
[^2.7.]*)
info "2.7.* Puppet deb package tied to Facter < 2.0.0, specifying Facter 1.7.4"
apt-get install -y puppet-common=$version-1puppetlabs1 puppet=$version-1puppetlabs1 facter=1.7.4-1puppetlabs1 --force-yes
;;
*)
apt-get install -y puppet-common=$version-1puppetlabs1 puppet=$version-1puppetlabs1 --force-yes
;;
esac
fi
What am I missing?
Full version of the script is here: https://github.com/petems/puppet-install-shell/blob/fix_puppet_agent_install/install_puppet_agent.sh

Answer 1

case ... esac in a POSIX shell script uses (glob-style) patterns, not regular expressions (while the two are distantly related, there are fundamental differences).
To get true regex matching in a sh script, you'd have to use expr with :, though it's probably not needed here.
To test for a prefix match, use <prefix>* in a case branch - case branches are always matched against the entire argument - no need for anchoring (which patterns don't support).
As an aside, what you're attempting would not even work for prefix matching as a regex. E.g., [^4.0.] is the same as [^.04] - i.e., a negated character class: it matches one character if it is neither . nor 0 nor 4.
When assigning to a variable in a POSIX shell script, do not use $.
To put it all together:
#/bin/sh
if [ "$version" = "" ]; then
version="latest";
info "Version parameter not defined, assuming latest"
else
info "Version parameter defined: $version";
info "Matching version to package version"
case "$version" in
4.0.*)
package_version='1.0.1'
;;
4.1.*)
package_version='1.1.1'
;;
4.2.*)
package_version='1.2.6'
;;
*)
critical "Unable to match requested version to package version"
exit 1
;;
esac
fi