configurable kill signals

config.example.toml

@@ -3,6 +3,9 @@ columns = 100
 rows = 30
 max_scrollback = 100000
 shell = "/bin/bash"
+# Signal sent to a pane's shell process when the pane is closed (e.g. ALT+X).
+# Use SIGKILL to force-kill instead of asking the shell to terminate.
+close_signal = "SIGTERM"
 font_family = "JetBrainsMono Nerd Font"
 font_size = 15
 

src/main/java/com/gregor/jprototerm/AppConfig.java

@@ -29,6 +29,7 @@ public record AppConfig(
         double windowHeight,
         boolean kittyGraphics,
         String scrollbackEditorCommand,
+        String closeSignal,
         Map<String, String> envOverride,
         Map<String, KeyBinding> keybindings
 ) {
@@ -71,6 +72,7 @@ public record AppConfig(
                     doubleValue(document, "window.height", defaults.windowHeight),
                     booleanValue(document, "kitty_graphics.enabled", defaults.kittyGraphics),
                     stringValue(document, "scrollback.editor_command", defaults.scrollbackEditorCommand),
+                    closeSignalValue(document, defaults.closeSignal),
                     envOverride(document, defaults.envOverride),
                     keybindings(document, defaults)
             );
@@ -92,6 +94,7 @@ public record AppConfig(
                 760.0,
                 true,
                 defaultScrollbackEditorCommand(),
+                "SIGTERM",
                 Map.of(),
                 Map.ofEntries(
                         Map.entry("navigate_left", KeyBinding.parse("ALT+H")),
@@ -125,11 +128,22 @@ public record AppConfig(
                 windowHeight,
                 kittyGraphics,
                 scrollbackEditorCommand,
+                closeSignal,
                 envOverride,
                 keybindings
         );
     }
 
+    /**
+     * The {@link #closeSignal} as a Linux signal number, sent to a pane's shell process when the
+     * pane is closed (e.g. via the close-pane key). Falls back to SIGTERM (15) if the configured
+     * name is somehow unresolvable.
+     */
+    public int closeSignalNumber() {
+        int number = LinuxPty.signalNumber(closeSignal);
+        return number < 0 ? 15 : number;
+    }
+
     public void save() {
         save(configPath(), this);
     }
@@ -156,6 +170,23 @@ public record AppConfig(
         return editor.trim() + " {file}";
     }
 
+    /**
+     * Reads {@code terminal.close_signal}, normalising it to a canonical {@code SIG*} name. An
+     * unknown or unset value keeps {@code fallback} so a typo can't leave a pane unkillable.
+     */
+    private static String closeSignalValue(TomlTable table, String fallback) {
+        String value = stringValue(table, "terminal.close_signal", null);
+        if (value == null) {
+            return fallback;
+        }
+        if (LinuxPty.signalNumber(value) < 0) {
+            System.err.println("Unknown terminal.close_signal '" + value + "', using " + fallback);
+            return fallback;
+        }
+        String normalized = value.trim().toUpperCase(java.util.Locale.ROOT);
+        return normalized.startsWith("SIG") ? normalized : "SIG" + normalized;
+    }
+
     private static Map<String, KeyBinding> keybindings(TomlTable table, AppConfig defaults) {
         Map<String, KeyBinding> parsed = new LinkedHashMap<>();
         for (String key : KEYBINDING_KEYS) {
@@ -193,6 +224,7 @@ public record AppConfig(
         builder.append("rows = ").append(rows).append('\n');
         builder.append("max_scrollback = ").append(maxScrollback).append('\n');
         builder.append("shell = ").append(quotedList(shell)).append('\n');
+        builder.append("close_signal = ").append(quoted(closeSignal)).append('\n');
         builder.append("font_family = ").append(quoted(fontFamily)).append('\n');
         builder.append("font_size = ").append(trimDouble(fontSize)).append("\n\n");
         builder.append("[window]\n");

src/main/java/com/gregor/jprototerm/LinuxPty.java

@@ -63,7 +63,10 @@ public final class LinuxPty implements AutoCloseable {
     private static final long TIOCSWINSZ = 0x5414L;
     private static final short POSIX_SPAWN_SETSID = 0x80;
     private static final int SIGHUP = 1;
+    private static final int SIGINT = 2;
+    private static final int SIGQUIT = 3;
     private static final int SIGKILL = 9;
+    private static final int SIGTERM = 15;
     private static final int WNOHANG = 1;
 
     // struct winsize { unsigned short ws_row, ws_col, ws_xpixel, ws_ypixel; }
@@ -105,11 +108,36 @@ public final class LinuxPty implements AutoCloseable {
     private final Object writeLock = new Object();
     private final int masterFd;
     private final int pid;
+    private final int closeSignal;
     private volatile boolean closed;
 
-    private LinuxPty(int masterFd, int pid) {
+    private LinuxPty(int masterFd, int pid, int closeSignal) {
         this.masterFd = masterFd;
         this.pid = pid;
+        this.closeSignal = closeSignal;
+    }
+
+    /**
+     * Resolves a signal name (e.g. {@code "SIGTERM"}, {@code "TERM"}, {@code "SIGKILL"}) to its
+     * Linux signal number, or {@code -1} if the name is not one we recognise. Case-insensitive and
+     * tolerant of a missing {@code SIG} prefix.
+     */
+    public static int signalNumber(String name) {
+        if (name == null) {
+            return -1;
+        }
+        String normalized = name.trim().toUpperCase(java.util.Locale.ROOT);
+        if (normalized.startsWith("SIG")) {
+            normalized = normalized.substring(3);
+        }
+        return switch (normalized) {
+            case "HUP" -> SIGHUP;
+            case "INT" -> SIGINT;
+            case "QUIT" -> SIGQUIT;
+            case "KILL" -> SIGKILL;
+            case "TERM" -> SIGTERM;
+            default -> -1;
+        };
     }
 
     /**
@@ -118,8 +146,10 @@ public final class LinuxPty implements AutoCloseable {
      * @param argv command and arguments (e.g. {@code {"/bin/zsh", "-i"}})
      * @param environment environment for the child, as KEY=VALUE pairs
      * @param workingDirectory directory the child starts in, or {@code null} to inherit
+     * @param closeSignal signal number sent to the child on {@link #close()} (e.g. SIGTERM)
      */
-    public static LinuxPty spawn(String[] argv, Map<String, String> environment, String workingDirectory) {
+    public static LinuxPty spawn(String[] argv, Map<String, String> environment, String workingDirectory,
+            int closeSignal) {
         Arena setup = Arena.ofConfined();
         try {
             int master = check(callInt(POSIX_OPENPT, O_RDWR | O_NOCTTY), "posix_openpt");
@@ -158,7 +188,7 @@ public final class LinuxPty implements AutoCloseable {
                     if (rc != 0) {
                         throw new IllegalStateException("posix_spawnp failed for " + argv[0] + " (rc=" + rc + ")");
                     }
-                    return new LinuxPty(master, pidOut.get(C_INT, 0));
+                    return new LinuxPty(master, pidOut.get(C_INT, 0), closeSignal);
                 } finally {
                     callInt(ATTR_DESTROY, attr);
                     callInt(FA_DESTROY, actions);
@@ -249,7 +279,7 @@ public final class LinuxPty implements AutoCloseable {
             return;
         }
         closed = true;
-        callKill(pid, SIGHUP);
+        callKill(pid, closeSignal);
         callInt(CLOSE, masterFd);
         reap();
         arena.close();

src/main/java/com/gregor/jprototerm/ShellSession.java

@@ -27,9 +27,10 @@ public final class ShellSession implements AutoCloseable {
      * config, not assumed here.
      */
     public static ShellSession start(List<String> shellCommand, Map<String, String> envOverride, TerminalPane pane,
-            int columns, int rows, String workingDirectory) {
+            int columns, int rows, String workingDirectory, int closeSignal) {
         try {
-            return spawn(shellCommand.toArray(new String[0]), envOverride, columns, rows, workingDirectory);
+            return spawn(shellCommand.toArray(new String[0]), envOverride, columns, rows, workingDirectory,
+                    closeSignal);
         } catch (RuntimeException ex) {
             pane.write("failed to start shell: " + ex.getMessage() + "\r\n");
             throw new IllegalStateException("Could not start shell " + String.join(" ", shellCommand), ex);
@@ -45,9 +46,10 @@ public final class ShellSession implements AutoCloseable {
      * flags. {@code command} must not be null.
      */
     public static ShellSession startCommand(Map<String, String> envOverride, TerminalPane pane,
-            int columns, int rows, String workingDirectory, String command) {
+            int columns, int rows, String workingDirectory, String command, int closeSignal) {
         try {
-            return spawn(new String[] {"/bin/sh", "-c", command}, envOverride, columns, rows, workingDirectory);
+            return spawn(new String[] {"/bin/sh", "-c", command}, envOverride, columns, rows, workingDirectory,
+                    closeSignal);
         } catch (RuntimeException ex) {
             pane.write("failed to run command: " + ex.getMessage() + "\r\n");
             throw new IllegalStateException("Could not run command: " + command, ex);
@@ -55,7 +57,7 @@ public final class ShellSession implements AutoCloseable {
     }
 
     private static ShellSession spawn(String[] argv, Map<String, String> envOverride,
-            int columns, int rows, String workingDirectory) {
+            int columns, int rows, String workingDirectory, int closeSignal) {
         Map<String, String> environment = new HashMap<>(System.getenv());
         environment.put("TERM", "xterm-kitty");
         environment.put("COLORTERM", "truecolor");
@@ -65,7 +67,8 @@ public final class ShellSession implements AutoCloseable {
         LinuxPty pty = LinuxPty.spawn(
                 argv,
                 environment,
-                workingDirectory != null ? workingDirectory : System.getProperty("user.home"));
+                workingDirectory != null ? workingDirectory : System.getProperty("user.home"),
+                closeSignal);
         ShellSession session = new ShellSession(pty);
         session.resize(columns, rows);
         return session;

src/main/java/com/gregor/jprototerm/TerminalPane.java

@@ -81,7 +81,7 @@ public final class TerminalPane implements AutoCloseable, RenderTarget {
             double widthPx, double heightPx, String workingDirectory) {
         TerminalPane pane = newPane(config, metrics, onContentChange, widthPx, heightPx);
         pane.attach(ShellSession.start(config.shell(), config.envOverride(), pane, pane.columns, pane.rows,
-                workingDirectory));
+                workingDirectory, config.closeSignalNumber()));
         return pane;
     }
 
@@ -94,7 +94,7 @@ public final class TerminalPane implements AutoCloseable, RenderTarget {
             double widthPx, double heightPx, String workingDirectory, String command) {
         TerminalPane pane = newPane(config, metrics, onContentChange, widthPx, heightPx);
         pane.attach(ShellSession.startCommand(config.envOverride(), pane, pane.columns, pane.rows,
-                workingDirectory, command));
+                workingDirectory, command, config.closeSignalNumber()));
         return pane;
     }