Output and errors

Output

stdout carries exactly the engine response, stderr everything else. operate guide output prints the full rules, also for XML, text and binary responses and --out-file.

• Format: JSON when stdout is not a terminal, a table on a terminal. -o json|table, OPERATE_OUTPUT or the profile setting override it. JSON is compact when piped and indented on a terminal or with --pretty.
• --fields id,name,variables.amount keeps only these properties (of every element of a list); in table format they are the columns.
• Tables without --fields show the identifying columns first and drop trailing columns to fit the terminal (120 characters when piped).
• No content (HTTP 204): stdout stays empty, stderr gets Done: <METHOD> <path> → 204 No Content.
• --dry-run prints the request instead of sending it; -o table prints only the curl command line:

$ operate process-definition start invoice --var amount=250 --dry-run
{"method":"POST","url":"http://localhost:8080/engine-rest/process-definition/key/invoice/start","headers":{"Accept":"application/json","Content-Type":"application/json"},"body":{"variables":{"amount":{"value":250,"type":"Integer"}}},"curl":"curl -X POST 'http://localhost:8080/engine-rest/process-definition/key/invoice/start' -H 'Accept: application/json' -H 'Content-Type: application/json' --data-raw '{\"variables\":{\"amount\":{\"value\":250,\"type\":\"Integer\"}}}'"}

$ operate task list --assignee demo --dry-run -o table
curl 'http://localhost:8080/engine-rest/task?assignee=demo' -H 'Accept: application/json'

• --verbose traces the request and response on stderr (secret headers masked):

$ operate process-definition list --key order-process --fields id,key,version --verbose
> GET http://localhost:8080/engine-rest/process-definition?key=order-process
> Accept: application/json
< 200 OK (14 ms, 408 bytes)
[{"id":"order-process:1:3910b506-c652-11f1-9fc4-1a2aceba9a9d","key":"order-process","version":1}]

Errors and exit codes

Errors go to stderr as one JSON line (-o table or a terminal prints readable text). hint names the fix (for unknown commands, options and body properties it starts with "Did you mean ...?"); engineMessage carries the engine's own explanation, also when the engine answers with plain text (such as JSON deserialization errors).

$ operate process-instance get abc
{"error":{"code":"NOT_FOUND","exitCode":5,"message":"HTTP 404 Not Found: Process instance with id abc does not exist","status":404,"engineType":"InvalidRequestException","engineMessage":"Process instance with id abc does not exist","hint":"Check the id or key. List the existing ones with `operate process-instance list`.","request":{"method":"GET","url":"http://localhost:8080/engine-rest/process-instance/abc"}}}

$ operate process-instance get abc -o table
Error: HTTP 404 Not Found: Process instance with id abc does not exist
  Engine: InvalidRequestException
  Request: GET http://localhost:8080/engine-rest/process-instance/abc
  Hint: Check the id or key. List the existing ones with `operate process-instance list`.

Fields: code, exitCode, message, and when available status, engineType, engineMessage, engineCode, hint, request (method, url) and data (e.g. the list of validation problems).

Exit	Meaning
0	success
1	internal error
2	usage error, invalid body (VALIDATION), READ_ONLY, CONFIRMATION_REQUIRED
3	configuration error, also an HTTP redirect (HTTP_REDIRECT)
4	401, 403, LOGIN_REQUIRED (a person must log in), LOGIN_FAILED, TOKEN_EXPIRED (a bearer token expired)
5	not found (404)
6	other 4xx: the engine rejected the request
7	engine error (5xx)
8	network error or timeout
9	expected state not reached (workflow commands): WAIT_TIMEOUT, INCIDENT, INSTANCE_ENDED, JOB_FAILED, CHECK_FAILED

Camunda 7 engines report many rule violations as HTTP 500 (exit 7), e.g. a task that is already completed or a deployment that still has running instances. Read engineMessage and fix the cause instead of retrying. A query value the engine cannot read (maxResults=abc) comes back as 404 QueryParamException; operate reports it as exit 6, not as a missing resource.

operate never follows redirects: a write redirected to a login page must not look successful, and credential headers must not travel to another host. A 3xx answer is the error HTTP_REDIRECT naming the target; point --url at the REST API root itself (e.g. https://).