Now this is very good news for us that are doing scripting with Salesforce DX. Currently the Salesforce DX CLI (sfdx) will send its output to stdout (standard out) when the command succeeds and to stderr (standard error) if the command fails. Why would a command fail? Well if you try and describe an org with a wrong or non-existing alias that’s one reason.
Now this is really the expected behaviour for a CLI but when doing scripting using the –json flag to always have the response returned as JSON it just makes it more complicated. For one the response already have a “status”-flag to indicate whether the invocation was successful or not. Secondly having to deal with stdout and stderr is not difficult but leads to boilerplate scripting code as what you really want to do is capture the response and check that “status”-flag in the JSON. Also it makes it harder to adopt for people new to CLI scripting and the way it’s done across platforms differ.
Now to the good news.
As of v44, there is an environment variable to have all JSON output go to stdout. Set SFDX_JSON_TO_STDOUT=true to get this new behaviour. This will become the default behaviour in v45. Now it’s not listed on the environment variables list for Salesforce DX yet but I trust it will be soon.