pty/run's busy names the program holding the terminal

busy said only that something ran. Where the host can tell (Linux, the
tty's foreground group's /proc comm, a new fg_name host call), it says
busy: <program> is running; elsewhere, busy as before. The GUI's host
gains the one small callback (render agent's file: gui.zig, fgName).

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

1 files changed, 15 insertions, 0 deletions

diff --git a/src/host_io.zig b/src/host_io.zig
index 10a85d8f..1db0dac9 100644
--- a/src/host_io.zig
+++ b/src/host_io.zig
@@ -25,6 +25,9 @@ pub const Host = struct {
         pty_signal: ?*const fn (ctx: ?*anyopaque, pane: u8, sig: pardes.PtySignal) void = null,
         close_pty: ?*const fn (ctx: ?*anyopaque, pane: u8) void = null,
         tty_taken: ?*const fn (ctx: ?*anyopaque, pane: u8) bool = null,
+        /// The name of the program holding the tty, when it is not the
+        /// shell (host_io.foregroundName), in `buf`.
+        fg_name: ?*const fn (ctx: ?*anyopaque, pane: u8, buf: []u8) ?[]const u8 = null,
         /// Answered at once, not queued as an effect: Kill asks while the
         /// job it saw running is still the one in the tty (host_io.killJob).
         kill_job: ?*const fn (ctx: ?*anyopaque, pane: u8) bool = null,
@@ -1751,6 +1754,18 @@ pub fn killJob(shell_pid: libc.pid_t, master_fd: c_int) bool {
     return libc.kill(-fg, libc.SIG.TERM) == 0;
 }
 
+/// The command name of the tty's foreground job, when that is not the
+/// shell: what `pty/run` says is running. Linux only (/proc/<pgrp>/comm).
+pub fn foregroundName(shell_pid: libc.pid_t, master_fd: c_int, buf: []u8) ?[]const u8 {
+    if (comptime builtin.os.tag != .linux) return null;
+    const fg = tcgetpgrp(master_fd);
+    if (fg <= 0 or fg == shell_pid) return null;
+    var name: [64:0]u8 = undefined;
+    const path = std.fmt.bufPrintSentinel(&name, "/proc/{d}/comm", .{@as(u32, @intCast(fg))}, 0) catch return null;
+    const comm = std.mem.trimEnd(u8, readProc(path, buf) orelse return null, "\n");
+    return if (comm.len > 0) comm else null;
+}
+
 fn readProc(path: [*:0]const u8, buf: []u8) ?[]const u8 {
     const fd = libc.open(path, .{ .ACCMODE = .RDONLY });
     if (fd < 0) return null;