The Debian program dpkg (available on all Debian and Ubuntu
installations) can compare two strings using the --compare-versions
option.
To use it, create a helper shell function (simply copy & paste the following snippet to your shell command-prompt):
compver() {
if dpkg --compare-versions "$1" lt "$2"
then printf '%s\n' "$1" "$2"
else printf '%s\n' "$2" "$1"
fi
}
Then compare two strings by calling compver:
$ compver 8.49 8.5 8.5 8.49
Note that dpkg will warn if the strings have invalid syntax:
$ compver "foo07.7z" "foo7a.7z"
dpkg: warning: version 'foo07.7z' has bad syntax:
version number does not start with digit
dpkg: warning: version 'foo7a.7z' has bad syntax:
version number does not start with digit
foo7a.7z
foo07.7z
$ compver "3.0/" "3.0.5"
dpkg: warning: version '3.0/' has bad syntax:
invalid character in version number
3.0.5
3.0/
To illustrate the different handling of hyphens between Debian and Coreutils algorithms (see Hyphen-minus ‘-’ and colon ‘:’):
$ compver abb ab-cd 2>/dev/null $ printf 'abb\nab-cd\n' | sort -V ab-cd abb abb ab-cd
To illustrate the different handling of file extension: (see Special handling of file extensions):
$ compver hello-8.txt hello-8.2.txt 2>/dev/null hello-8.2.txt hello-8.txt $ printf '%s\n' hello-8.txt hello-8.2.txt | sort -V hello-8.txt hello-8.2.txt