Script collection to calculate colours from hostnames.
For a given string (hostname) a value in the range 18-229 is calculated, that could be used as an 8-bit colour value. A script should always calculate the same values for the same input.
It uses a md5-hash of the given string (hostname) to determine a value. Only the first two bytes are used and there are only 66 colour families, so there are a lot of collisions.
One example of its use is colour coding a command prompt to not mix up machines: It can be integrated in any provisioning scripts for vms, jails or containers.
You can run the scripts from a shell.
./hostcolor.sh --help
./hostcolor.sh [-n] [-p] [-s salt] hostname [hostname [hostname [...]]]
./hostcolor.sh [--pretty-print] [--salt=salt] hostname [hostname [hostname [...]]]From the in-script documentation:
Takes [hostname] = [label] + [number] (e.g. dns1 or web7) and calculates
a color (256 Format) for shell use. Color range is 18-229. Only last char
of [number] is used, null is treated as 0.
This works well for [number] 0-2 and ok up to 3. After that there might be
collisions. There are up to 66 color families with 3 destinct colors if all
families stay under 4 members. (e.g. fam0 22-24 and fam1 25-27 overlap
when the family 0 has a fourth member: fam0-4 is 25).
Notice: abc32xyz1 is interpreted as lable = "abcxyz" number = "321"
Families have a head, defining the name (i.e. fam53), the head is allways
member #1, not #0. This family name is fam[0-66] and the color of the head
is calculated by [0-66] * 3 + 23 - so fam0-1 is 23 and fam66-1 is 221.
Even number families count up and jump down after member #5 and continue
decending until member #9. Odd number families vice versa. The col of any
familiy member can be calculated as famX-1 col + mod. The mod is obtained
using the member number. The following table elaborates on this:
mem col mod mem col mod
fam0-0 22 -1 = mem-1 fam55-0 189 +1 = (mem-1) *-1
1 23 +0 = mem-1 1 188 +0 = (mem-1) *-1
0 2 24 +1 = mem-1 5 2 187 -1 = (mem-1) *-1
3 25 +2 = mem-1 5 3 186 -2 = (mem-1) *-1
^ 4 26 +3 = mem-1 4 185 -3 = (mem-1) *-1
E 5 27 +4 = mem-1 ^ 5 184 -4 = (mem-1) *-1
V 6 21 -2 = (mem-4) *-1 O 6 190 +2 = mem-4
E 7 20 -3 = (mem-4) *-1 D 7 191 +3 = mem-4
N 8 19 -4 = (mem-4) *-1 D 8 192 +4 = mem-4
9 18 -5 = (mem-4) *-1 9 193 +5 = mem-4
Notice: The sh and py versions of host-color have a slight math. varinace
and are not to be used interchangebly (e.g. web1 sh->50 and py->53).
-> don't like the colors - use the --salt (-s) to modyfiy.
-h --help show the version, usage and in-script documentation only.
-n --no-newline do not print a linebreak after each output.
% ./hostcolor.sh -n test foo1 foo2
27 155 156-p --pretty-print print a table displaying the colour, its number and the tinted hostname.
% ./hostcolor.sh -p test foo1 foo2
▒▒▒▒ 27 test
████ 155 foo1
▓▓▓▓ 156 foo2 …kinda silly without colour.
-s= --salt= add a salt to the hostnames in case you don't like the colors suggested
% ./hostcolor.sh test foo1 foo2
27
155
156% ./hostcolor.sh --salt=spice test foo1 foo2
160
209
210Default behaviour, uses line breaks.
% ./hostcolor.sh test | xxd
00000000: 3237 0a 27.Suppressing new lines leads to the use of separators.
% ./hostcolor.sh -n test | xxd
00000000: 3237 20 27The separator used may vary depending on the underlying system.
As of version 1.2 there are debug statements on lines 90sh and 107py that are commented out.
As some jurisdictions require a licence, we have opted for Creative Commons Zero v1.0 Universal.