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Sorting by fields

This is not easy to understand from the manpages
But to sort by 3'rd then 2rd, and then 1st field...

  sort -t: -k3,3 -k2,2 -k1,1   /etc/passwd

If second field are numbers...

  sort -t: -k3,3 -k2,2n -k1,1   /etc/passwd

If the field number is NOT repeated, it goes from that field to EOL

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Sorting - Human readable units

  sort using numbers with letter suffix  (eg  265Kbytes, without space!)
     sort -h

  EG:
     du -sh * | sort -rh


FYI: convert numbers to si (base 1000) or iec (base 1024) units

     numfmt --to=si 4096
     4.1K

     numfmt --to=iec 4096
     4.0K

     numfmt --to=iec-i 4096
     4.0Ki

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Sort Internet Addresses (IPs)

This makes things tricky, as numerical sorting treats '.' as a decimal
and not as a field separator.

Old method before "Semantic Versioning"
     sort -n -t . -k 1,1 -k 2,2 -k 3,3 -k 4,4

Semantic Versioning can sort IP's
     sort -V

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Sorting Version Numbers

See "Semantic Versioning"  https://semver.org/

Sorting Version numbers with '.' separations are tricky...

  sort

    kernel-1.13.4
    kernel-1.3.17
    kernel-1.3.7
    kernel-1.3.8
    kernela-2.0.0
    kernelb-0.0.1

  sort -V

    kernela-2.0.0
    kernelb-0.0.1
    kernel-1.3.7
    kernel-1.3.8
    kernel-1.3.17
    kernel-1.13.4

It worked but...
Note how the name aspects are not sorted in the same order as before.
There is not even a gurantee that 'a' and 'b' are in that order!

The fix is to seperate the name and version fields...
EG sort by name first, then version number

  sort -t- -k1,1d -k2V

    kernel-1.3.7
    kernel-1.3.8
    kernel-1.3.17
    kernel-1.13.4
    kernela-2.0.0
    kernelb-0.0.1

----
Version sorting is also available using "ls -v"

  ls -1v  /usr/src/kernels/

    4.16.8-300.fc28.x86_64/
    4.16.12-300.fc28.x86_64/
    4.17.7-200.fc28.x86_64/

But with names present it produces the same 'name' ordering problem,
but unlike "sort", "ls" can not specify multiple sort fields.

  ls -1v version_test_dir/

    kernela-2.0.0
    kernelb-0.0.1
    kernel-1.3.7
    kernel-1.3.8
    kernel-1.3.17
    kernel-1.13.4

Solution for filenames...

  ls -1 version_test_dir/ | sort -t- -k1,1d -k2V | column

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Version number testing
https://stackoverflow.com/questions/4023830/

This uses -C to quietly check for sorted order.RNING
True if second line is 'same or newer' than first

  version_test() { printf '%s\n' "$@" | sort -C -V; }
  # version_test  {minimim_desired_version} {installed_version}
  # FALSE if an update is needed

  # Testing Version Numbers
  # order below is sorted order from "sort -V"
  echo '
    # Older Version
    | 0
    | 0.1.1.2
    | 0.9.8
    | 1.0.0d
    | 1.0.1
    | 1.0.1a
    | 1.0.1k
    | 1.0.2g
    | 1.0.2k-fips
    | 1.1.1
    | 0001.0001.0001a
    | 1.1.1a
    | 1.1.1a.2
    # Same or Newer
    | 1.1.1b
    | 0001.0001.0001k
    | 1.1.1k
    | 1.1.1k-fips
    | 1.1.1.1
    | 1.1.1.2
    | 1.2
    | 2
    ' | sed -n '/^ *|/!d; s///; s/^ //; p' |
    while read -r v; do
      if  version_test 1.1.1b "$v"
      then printf "%-20s%s\n" "$v" "NEWER (or at least the same)"
      else printf "%-20s%s\n" "$v" "OLDER"
      fi
    done

Test can also be used for 'between version' testing

  version_test {minimum_version} {current_version} {maximum_version}

WARNING: 
  version_test 01.01.01 1.1.1 && echo true || echo false
  # > true
  version_test 1.1.1 01.01.01 && echo true || echo false
  # > false

Numerically they are the same, but not to version as they sort differently

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