How to fill/change particular unknown strings of some sections of a well formated JSON file from bash keeping the format intact? - json

Question

How to fill/change particular unknown strings of some sections of a well formated .json file from bash keeping the format intact ?
Details:
Part of settings.json :
"profiles":
{
"defaults":
{
// Put settings here that you want to apply to all profiles.
},
"theme": "dark",
"list":
[
{
// Make changes here to the powershell.exe profile.
"guid": "{61c54bbd-c2c6-5271-96e7-009a87ff44bf}",
"name": "Windows PowerShell",
"commandline": "powershell.exe",
"hidden": false,
"acrylicOpacity": 0.9,
"colorScheme" : "Material",
"cursorColor" : "#FFFFFD",
"useAcrylic" : true
},
{
// Make changes here to the cmd.exe profile.
"guid": "{0caa0dad-35be-5f56-a8ff-afceeeaa6101}",
"name": "Command Prompt",
"commandline": "cmd.exe",
"hidden": false,
"acrylicOpacity": 0.2,
"colorScheme" : "Frost",
"cursorColor" : "#000000",
"useAcrylic": true,
},
"schemes": [
{
"name" : "Frost",
"background" : "#ffffff",
"black" : "#3C5712",
"blue" : "#17b2ff",
"brightBlack" : "#749B36",
"brightBlue" : "#27B2F6",
"brightCyan" : "#13A8C0",
"brightGreen" : "#89AF50",
"brightPurple" : "#F2A20A",
"brightRed" : "#F49B36",
"brightWhite" : "#741274",
"brightYellow" : "#991070",
"cyan" : "#3C96A6",
"foreground" : "#000000",
"green" : "#6AAE08",
"purple" : "#991070",
"red" : "#8D0C0C",
"white" : "#6E386E",
"yellow" : "#991070"
},
another file pickcolor.txt:
#FFFAFA
#FFFAFA
#EEE9E9
#FFC1C1
#EEB4B4
#CDC9C9
#F08080
#FF6A6A
#CD9B9B
#EE6363
#BC8F8F
#FF4040
#FF3030
#EE3B3B
#CD5C5C
#CD5555
#EE2C2C
#8B8989
#CD3333
#FF0000
#FF0000
#8B6969
#CD2626
#EE0000
#B22222
#A52A2A
#CD0000
#8B3A3A
#8B2323
Want to create a bash which changes value of fields like "background", "cursorColor" to any random value from pickcolor.txt
Requirements/problems I am facing:
Fields appearing many times gets different values from each other
Value of fields changes from time to time, so simple find and replace do not work
Fields changes there line number every time new contents are added, so line number for fields do not remain same.
Format of .json file should not change
Please note : I do not want anyone to write the complete code ; just hinting/pointing out ways will be sufficient. And thanks in advance !!

Answer 1

I believe what you need is something like this
fields=(background cursorColor)
colors=("#FFFAFA" "#CDC9C9" "#EE3B3B")
size=${#colors[#]}
for f in "${fields[#]}"; do
for line in $(grep -n "\"$f\"" myfile.json | cut -f1 -d:); do
index=$(($RANDOM % $size))
color="${colors[$index]}"
sed -i $line's|\("'"$f"'"\s*:\s*"\).\+"|\1'"$color"'"|' myfile.json
done
done
There is some magic in this solution:
We choose random index from array of colors
For each of fields which should be replaced we create it's own unique sed expression, which
First part (\("'"$f"'"\s*:\s*"\)#.\+" finds anything matching pattern "<field name>"<spaces>:<spaces>"<any color>"
Captures anything until 3rd double quote into group
In second group (\1'"${colors[$index]}"'") replaces matched part with itself, but inserts randomly picked color from array into second double quote group
Weird things with lots of quotes are made to interpolate field name and color into single quotes
NB: this is tested with GNU sed. May need a bit different syntax for BSD