Only a write logs an err: a refused open or truncation, create or remove, or a write to pane/new, is its error alone, and every refusal is said in words

The one-failure rule is a write's. A refused remove, pane/new's open refused for want of a slot, and an OTRUNC open's refused truncation (data's after a failed addr) also logged an err, and a reply carrying only an errno reached the client as the C library's text (Operation not permitted). tree.handle now gives such a reply Plan 9's words, chosen so 9ns maps each back to its errno (EPERM's to EACCES, as Plan 9's does), and serveFs logs errs for writes only, not a write to pane/new, which is only read. docs/fs.md and the 9P skill say so, and that a look miss quotes what was written.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

1 files changed, 3 insertions, 2 deletions

diff --git a/src/ninep/cols.zig b/src/ninep/cols.zig
index 6b59f9e5..cc583c93 100644
--- a/src/ninep/cols.zig
+++ b/src/ninep/cols.zig
@@ -368,10 +368,11 @@ test "a column's ctl and exec act on it as its tag would, and rmdir closes it on
     try testing.expectEqual(E.INVAL, th.wr(p, Node.ofCol(empty, .ctl), "Exit\n").errno());
     var rec: [64]u8 = undefined;
     try testing.expect(th.logHas(p, try std.fmt.bufPrint(&rec, "err - col/{d}/ctl: unknown control message \"Exit\"", .{empty})));
-    // rmdir refuses a column with a pane, and says why.
+    // rmdir refuses a column with a pane, and says why, in its error alone.
     const full = th.call(p, .{ .tag = 1, .op = .release, .node = Node.ofCol(empty, .dir), .remove = true });
     try testing.expectEqual(E.NOTEMPTY, full.errno());
-    try testing.expect(th.logHas(p, try std.fmt.bufPrint(&rec, "err - col/{d}: column not empty", .{empty})));
+    try testing.expect(std.mem.startsWith(u8, full.reply.ename, "column not empty"));
+    try testing.expect(!th.logHas(p, try std.fmt.bufPrint(&rec, "err - col/{d}: column not empty", .{empty})));
     // exec runs a word as a click in that column's tag: Delcol closes it.
     try testing.expectEqual(tree.Status.ok, th.wr(p, Node.ofCol(empty, .exec), "Delcol\n").reply.status);
     try testing.expectEqual(@as(?usize, null), layout.columnBySerial(p, empty));