A column has a ctl, an exec and an rmdir over 9P, and Restore maps its serial

A script could read and write a column's tag but not act on the column.
col/<serial>/ctl takes Delcol, Joincol, New and Tty, each acting on that
column as from its tag; col/<serial>/exec runs a word as a middle click in
the tag; rmdir col/<serial> closes an empty column and refuses one with
panes (ENOTEMPTY, an err record saying why). The root ctl's refusal of
Delcol and Joincol points at col/<serial>/ctl. A dump keeps each column's
serial and Restore logs restoredcol <old> <new>; the dump golden gains
them. Documented: Joincol's survivor, the column on the right, keeps its
serial and tag.

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

1 files changed, 30 insertions, 8 deletions

diff --git a/src/ninep/tree.zig b/src/ninep/tree.zig
index c4ade1f7..baf8c772 100644
--- a/src/ninep/tree.zig
+++ b/src/ninep/tree.zig
@@ -272,7 +272,16 @@ pub const PaneFile = enum(u5) {
 /// /col/<serial> and its tag: a column is named by its serial, which stays
 /// while it lives as a pane's does; this bit, past a pane serial's 32, keeps
 /// the two apart.
-pub const ColFile = enum(u5) { dir = 0, tag = 1 };
+pub const ColFile = enum(u5) {
+    dir = 0,
+    tag = 1,
+    ctl = 2,
+    exec = 3,
+
+    pub fn fileName(f: ColFile) []const u8 {
+        return @tagName(f);
+    }
+};
 const col_bit: u59 = 1 << 58;
 
 pub const Node = packed struct(u64) {
@@ -454,10 +463,14 @@ fn attrOf(p: *Pardes, target: Target) ?Reply.Attr {
         .col => |c| {
             if (layout.columnBySerial(p, c.serial) == null) return null;
             return .{
-                .name = if (c.file == .dir) (std.fmt.bufPrint(&p.fs.node_name, "{d}", .{c.serial}) catch unreachable) else "tag",
+                .name = if (c.file == .dir) (std.fmt.bufPrint(&p.fs.node_name, "{d}", .{c.serial}) catch unreachable) else c.file.fileName(),
                 .node = Node.ofCol(c.serial, c.file),
                 .dir = c.file == .dir,
-                .mode = if (c.file == .dir) 0o755 else 0o666,
+                .mode = switch (c.file) {
+                    .dir => 0o755,
+                    .ctl, .exec => 0o222,
+                    .tag => 0o666,
+                },
                 .size = if (c.file == .tag) cols.headerText(p, c.serial).?.len + 1 else 0,
                 .mtime = p.fs.started,
                 .append = c.file == .tag,
@@ -562,8 +575,9 @@ fn lookup(p: *Pardes, req: Req, target: Target) Reply {
         },
         .col => |c| col: {
             if (c.file != .dir) return Reply.fail(req.tag, E.NOTDIR);
-            if (!std.mem.eql(u8, name, "tag")) return Reply.fail(req.tag, E.NOENT);
-            break :col Node.ofCol(c.serial, .tag);
+            const f = std.meta.stringToEnum(ColFile, name) orelse return Reply.fail(req.tag, E.NOENT);
+            if (f == .dir) return Reply.fail(req.tag, E.NOENT);
+            break :col Node.ofCol(c.serial, f);
         },
         .pane => |t| pane: {
             _ = p.paneBySerial(t.serial) orelse return Reply.fail(req.tag, E.NOENT);
@@ -638,7 +652,9 @@ fn readdir(p: *Pardes, req: Req, target: Target) Reply {
         .col => |c| {
             if (layout.columnBySerial(p, c.serial) == null) return Reply.fail(req.tag, E.NOENT);
             if (c.file != .dir) return Reply.fail(req.tag, E.NOTDIR);
-            if (skip > 0) skip -= 1 else stageDirent(out, p.gpa, Node.ofCol(c.serial, .tag), false, "tag");
+            inline for (.{ ColFile.tag, ColFile.ctl, ColFile.exec }) |f| {
+                if (skip > 0) skip -= 1 else stageDirent(out, p.gpa, Node.ofCol(c.serial, f), false, f.fileName());
+            }
         },
         .pane => |t| {
             const id = p.paneBySerial(t.serial) orelse return Reply.fail(req.tag, E.NOENT);
@@ -729,7 +745,8 @@ fn remove(p: *Pardes, req: Req) Reply {
     const target = Node.target(req.node) orelse return Reply.fail(req.tag, E.NOENT);
     const t = switch (target) {
         .pane => |t| t,
-        .top, .col => return Reply.fail(req.tag, E.PERM),
+        .top => return Reply.fail(req.tag, E.PERM),
+        .col => |c| return cols.remove(p, req, c.serial, c.file),
     };
     if (t.file != .dir) return Reply.fail(req.tag, E.PERM);
     const id = p.paneBySerial(t.serial) orelse return Reply.fail(req.tag, E.NOENT);
@@ -902,7 +919,12 @@ fn write(p: *Pardes, req: Req, target: Target) Reply {
             if (t.file.inPty() and !pn.isTerminal()) return Reply.fail(req.tag, E.NOENT);
             return pane.write(p, req, id, pn, t.file);
         },
-        .col => |c| return if (c.file == .tag) cols.write(p, req, c.serial) else Reply.fail(req.tag, E.PERM),
+        .col => |c| return switch (c.file) {
+            .tag => cols.write(p, req, c.serial),
+            .ctl => cols.writeCtl(p, req, c.serial),
+            .exec => cols.writeExec(p, req, c.serial),
+            .dir => Reply.fail(req.tag, E.PERM),
+        },
     }
 }