Gnu/coreutils/Comparing-two-strings-using-Debian 0027s-algorithm
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30.4.1 Comparing two strings using Debian’s algorithm
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() { dpkg --compare-versions "$1" lt "$2" \ && printf "%s\n" "$1" "$2" \ || printf "%s\n" "$2" "$1" ; \ }
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 Minus/Hyphen and Colon characters):
$ 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