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coreutils: Comparing two strings using Debian's algorithm

 
 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
 
 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
 

Info Catalog coreutils: Advanced Topics coreutils: Reporting bugs or incorrect results