1 files changed, 20 insertions, 0 deletions
diff --git a/packages/meshbay-cli/src/meshbay_cli/output.py b/packages/meshbay-cli/src/meshbay_cli/output.py
index 75a54ff..d4c0758 100644
--- a/packages/meshbay-cli/src/meshbay_cli/output.py
+++ b/packages/meshbay-cli/src/meshbay_cli/output.py
@@ -138,3 +138,23 @@ class Progress:
 def sentence(text: str) -> str:
     """The first letter up, the rest untouched: `str.capitalize` turns -R into -r."""
     return text[:1].upper() + text[1:]
+
+
+def confirm(question: str, yes: bool) -> None:
+    """
+    Go on only on a yes: `--yes`, or `y` typed at a terminal. With neither — a
+    script that did not say so — refuse before anything is sent, rather than
+    take silence for consent.
+    """
+    from .errors import USAGE, CliError
+    if yes:
+        return
+    if not sys.stdin.isatty():
+        raise CliError(USAGE, f"{question} Not done: there is no terminal to ask on; "
+                              "pass --yes to confirm.")
+    # On stderr, like every other word to the person: stdout is the result.
+    sys.stderr.write(f"{question} [y/N] ")
+    sys.stderr.flush()
+    answer = sys.stdin.readline()
+    if answer.strip().lower() not in ("y", "yes"):
+        raise CliError(USAGE, "Not done.")