batch file, read json file into string

Question

I need to read a json file:

{
   "key": {
       "subkey": "value"
   }
}

so I can pass it as an argument to a command:

program -e SETTINGS=<JSON FILE AS STRING>

Answer 1

Combining the answers to these questions...

• How to read entire content of a text file in batch
• Escape “double quotes” inside batch's input parameters

... we can write the following batch file:

:: Make it possible to read immediate value of variable using !variable! syntax.
setlocal enabledelayedexpansion

:: Read file "test.json" into variable data, removing line breaks.
set data=
for /f "delims=" %%x in (test.json) do set "data=!data!%%x"

:: Escape double quotes in data
set data=%data:"=\"%

:: Finally call program with the entire content of the JSON file as parameter
program -e "SETTINGS=%data%"

Note that when using the cmd.exe command processor, the maximum length for a commandline and also for environment variables is 8191 characters, so this will obviously restrict the maximum size of the JSON file you can pass.