command: use MaCommand object

4 files changed, 610 insertions, 134 deletions

diff --git a/command/Makefile.am b/command/Makefile.am
index 76fe2497..2a9115d9 100644
--- a/command/Makefile.am
+++ b/command/Makefile.am
@@ -8,7 +8,7 @@ AM_CPPFLAGS = \
 APPLET_LOCATION = $(libexecdir)/command-applet
 
 libexec_PROGRAMS = command-applet
-command_applet_SOURCES = command.c
+command_applet_SOURCES = command.c ma-command.c ma-command.h
 command_applet_LDADD = $(MATE_APPLETS4_LIBS) $(MATEDESKTOP_LIBS)
 command_applet_CFLAGS = $(WARN_CFLAGS)
 
diff --git a/command/command.c b/command/command.c
index 2cd3c00c..f62f2325 100644
--- a/command/command.c
+++ b/command/command.c
@@ -32,6 +32,7 @@
 
 #include <mate-panel-applet.h>
 #include <mate-panel-applet-gsettings.h>
+#include "ma-command.h"
 
 /* Applet constants */
 #define APPLET_ICON    "utilities-terminal"
@@ -54,14 +55,15 @@ typedef struct
     MatePanelApplet   *applet;
 
     GSettings         *settings;
-    GPid               child_pid;
-    gchar             *buffer;
 
     GtkLabel          *label;
     GtkImage          *image;
     GtkBox            *box;
+    MaCommand         *command;
+    GCancellable      *cancellable;
+    gboolean           running;
 
-    gchar             *command;
+    gchar             *cmdline;
     gint               interval;
     gint               width;
 
@@ -71,6 +73,11 @@ typedef struct
 static void command_about_callback (GtkAction *action, CommandApplet *command_applet);
 static void command_settings_callback (GtkAction *action, CommandApplet *command_applet);
 static gboolean command_execute (CommandApplet *command_applet);
+static gboolean command_text_changed (GtkWidget *widget, GdkEvent  *event, gpointer user_data);
+static void interval_value_changed (GtkSpinButton *spin_button, gpointer user_data);
+static void width_value_changed (GtkSpinButton *spin_button, gpointer user_data);
+static void command_async_ready_callback (GObject *source_object, GAsyncResult *res, gpointer user_data);
+static gboolean timeout_callback (CommandApplet *command_applet);
 
 static const GtkActionEntry applet_menu_actions [] = {
     { "Preferences", "document-properties", N_("_Preferences"), NULL, NULL, G_CALLBACK (command_settings_callback) },
@@ -91,22 +98,15 @@ command_applet_destroy (MatePanelApplet *applet_widget, CommandApplet *command_a
         command_applet->timeout_id = 0;
     }
 
-    if (command_applet->command != NULL)
-    {
-        g_free (command_applet->command);
-        command_applet->command = NULL;
-    }
-
-    if (command_applet->child_pid != 0)
+    if (command_applet->cmdline != NULL)
     {
-        g_spawn_close_pid (command_applet->child_pid);
-        command_applet->child_pid = 0;
+        g_free (command_applet->cmdline);
+        command_applet->cmdline = NULL;
     }
 
-    if (command_applet->buffer != NULL)
+    if (command_applet->command != NULL)
     {
-        g_free (command_applet->buffer);
-        command_applet->buffer = NULL;
+        g_object_unref (command_applet->command);
     }
 
     g_object_unref (command_applet->settings);
@@ -127,7 +127,56 @@ command_about_callback (GtkAction *action, CommandApplet *command_applet)
                           "comments", _("Shows the output of a command"),
                           "translator-credits", _("translator-credits"),
                           "logo-icon-name", APPLET_ICON,
-    NULL );
+                          NULL );
+}
+
+static gboolean
+command_text_changed (GtkWidget *widget, GdkEvent  *event, gpointer user_data)
+{
+    const gchar *text;
+    CommandApplet *command_applet;
+
+    command_applet = (CommandApplet*) user_data;
+    text = gtk_entry_get_text (GTK_ENTRY(widget));
+    if (g_strcmp0(command_applet->cmdline, text) == 0) {
+        return TRUE;
+    }
+
+    if (strlen (text) == 0) {
+        gtk_label_set_text (command_applet->label, ERROR_OUTPUT);
+        return TRUE;
+    }
+
+    g_settings_set_string (command_applet->settings, COMMAND_KEY, text);
+    return TRUE;
+}
+
+static void interval_value_changed (GtkSpinButton *spin_button, gpointer user_data)
+{
+    gint value;
+    CommandApplet *command_applet;
+
+    command_applet = (CommandApplet*) user_data;
+    value = gtk_spin_button_get_value_as_int (spin_button);
+    if (command_applet->interval == value) {
+        return;
+    }
+
+    g_settings_set_int (command_applet->settings, INTERVAL_KEY, value);
+}
+
+static void width_value_changed (GtkSpinButton *spin_button, gpointer user_data)
+{
+    gint value;
+    CommandApplet *command_applet;
+
+    command_applet = (CommandApplet*) user_data;
+    value = gtk_spin_button_get_value_as_int (spin_button);
+    if (command_applet->width == value) {
+        return;
+    }
+
+    g_settings_set_int (command_applet->settings, WIDTH_KEY, value);
 }
 
 /* Show the preferences dialog */
@@ -186,10 +235,13 @@ command_settings_callback (GtkAction *action, CommandApplet *command_applet)
 
     g_signal_connect (dialog, "response", G_CALLBACK (gtk_widget_destroy), dialog);
 
+    g_signal_connect(command, "focus-out-event", G_CALLBACK (command_text_changed), command_applet);
+    g_signal_connect(interval, "value-changed", G_CALLBACK (interval_value_changed), command_applet);
+    g_signal_connect(width, "value-changed", G_CALLBACK (width_value_changed), command_applet);
     /* use g_settings_bind to manage settings */
-    g_settings_bind (command_applet->settings, COMMAND_KEY, command, "text", G_SETTINGS_BIND_DEFAULT);
-    g_settings_bind (command_applet->settings, INTERVAL_KEY, interval, "value", G_SETTINGS_BIND_DEFAULT);
-    g_settings_bind (command_applet->settings, WIDTH_KEY, width, "value", G_SETTINGS_BIND_DEFAULT);
+    g_settings_bind (command_applet->settings, COMMAND_KEY, command, "text", G_SETTINGS_BIND_GET_NO_CHANGES);
+    g_settings_bind (command_applet->settings, INTERVAL_KEY, interval, "value", G_SETTINGS_BIND_GET_NO_CHANGES);
+    g_settings_bind (command_applet->settings, WIDTH_KEY, width, "value", G_SETTINGS_BIND_GET_NO_CHANGES);
     g_settings_bind (command_applet->settings, SHOW_ICON_KEY, showicon, "active", G_SETTINGS_BIND_DEFAULT);
 
     gtk_widget_show_all (GTK_WIDGET (dialog));
@@ -199,17 +251,27 @@ command_settings_callback (GtkAction *action, CommandApplet *command_applet)
 static void
 settings_command_changed (GSettings *settings, gchar *key, CommandApplet *command_applet)
 {
-    gchar *command;
+    GError *error = NULL;
+    gchar *cmdline;
+    gchar **argv;
 
-    command = g_settings_get_string (command_applet->settings, COMMAND_KEY);
+    cmdline = g_settings_get_string (command_applet->settings, COMMAND_KEY);
+    if (strlen (cmdline) == 0 || g_strcmp0(command_applet->cmdline, cmdline) == 0)
+        return;
+
+    if (!g_shell_parse_argv (cmdline, NULL, &argv, &error))
+    {
+        gtk_label_set_text (command_applet->label, ERROR_OUTPUT);
+        g_clear_error (&error);
+        return;
+    }
+    g_strfreev(argv);
 
-    if (command_applet->command)
-        g_free (command_applet->command);
+    if (command_applet->cmdline)
+        g_free (command_applet->cmdline);
+    command_applet->cmdline = cmdline;
 
-    if (command != NULL && command[0] != 0)
-        command_applet->command = command;
-    else
-        command_applet->command = g_strdup ("");
+    command_execute (command_applet);
 }
 
 static void
@@ -219,10 +281,9 @@ settings_width_changed (GSettings *settings, gchar *key, CommandApplet *command_
 
     width = g_settings_get_int (command_applet->settings, WIDTH_KEY);
 
-    command_applet->width = width;
-
-    /* execute command to start new timer */
-    command_execute (command_applet);
+    if (command_applet->width != width) {
+        command_applet->width = width;
+    }
 }
 
 static void
@@ -236,23 +297,18 @@ settings_interval_changed (GSettings *settings, gchar *key, CommandApplet *comma
     if (interval < 1)
         interval = 1;
 
-    command_applet->interval = interval;
-
-    /* stop current timer */
-    if (command_applet->timeout_id != 0)
-    {
-        g_source_remove (command_applet->timeout_id);
-        command_applet->timeout_id = 0;
+    if (command_applet->interval == interval) {
+        return;
     }
+    command_applet->interval = interval;
 
-    /* execute command to start new timer */
     command_execute (command_applet);
 }
 
 static void
 process_command_output (CommandApplet *command_applet, gchar *output)
 {
-    gtk_widget_set_tooltip_text (GTK_WIDGET (command_applet->label), command_applet->command);
+    gtk_widget_set_tooltip_text (GTK_WIDGET (command_applet->label), command_applet->cmdline);
 
     if ((output == NULL) || (output[0] == '\0'))
     {
@@ -301,121 +357,82 @@ process_command_output (CommandApplet *command_applet, gchar *output)
     }
 }
 
-static gboolean
-stdout_io_func (GIOChannel *ioc, GIOCondition cond, gpointer data)
+static void command_async_ready_callback (GObject *source_object, GAsyncResult *res, gpointer user_data)
 {
+    gchar *output;
+    GError *error = NULL;
     CommandApplet *command_applet;
 
-    command_applet = data;
-    if (cond & (G_IO_IN | G_IO_PRI))
-    {
-        if (strlen (command_applet->buffer) == 0)
-        {
-            GError *error = NULL;
-            GIOStatus  ret;
-            gsize      len = 0;
+    command_applet = (CommandApplet*) user_data;
 
-            ret = g_io_channel_read_chars (ioc, command_applet->buffer, command_applet->width, &len, &error);
-            if (len <= 0 || ret != G_IO_STATUS_NORMAL)
-            {
-                g_clear_error (&error);
-                return FALSE;
-            }
-            process_command_output (command_applet, command_applet->buffer);
+    output = ma_command_run_finish (command_applet->command, res, &error);
+    if (error == NULL) {
+        process_command_output (command_applet, output);
+    } else {
+        if (!g_error_matches (error, G_IO_ERROR, G_IO_ERROR_FAILED)) {
+            gtk_label_set_text (command_applet->label, ERROR_OUTPUT);
         }
-        return FALSE;
+        g_error_free (error);
     }
-
-    if (cond & (G_IO_ERR | G_IO_HUP | G_IO_NVAL))
-        return FALSE;
-
-    return TRUE;
+    g_free (output);
+    command_applet->running = FALSE;
 }
 
-static void
-on_child_exit (GPid child_pid, gint status, gpointer data)
+static gboolean timeout_callback (CommandApplet *command_applet)
 {
-    CommandApplet *command_applet;
-
-    command_applet = data;
-    g_spawn_close_pid (child_pid);
-    command_applet->child_pid = 0;
-}
-
-static void
-set_up_io_channel (gint fd, GIOCondition cond, GIOFunc func, gpointer data)
-{
-    GIOChannel *ioc;
-
-    ioc = g_io_channel_unix_new (fd);
-
-    g_io_channel_set_encoding (ioc, NULL, NULL);
-    g_io_channel_set_buffered (ioc, FALSE);
-
-    g_io_channel_set_close_on_unref (ioc, TRUE);
+    /* command is empty, wait for next timer execution */
+    if (strlen (command_applet->cmdline) == 0) {
+        return G_SOURCE_CONTINUE;
+    }
 
-    g_io_add_watch (ioc, cond, func, data);
-    g_io_channel_unref (ioc);
+    /* command running, wait for next timer execution */
+    if (command_applet->running) {
+        return G_SOURCE_CONTINUE;
+    } else {
+        gchar **argv;
+        GError *error = NULL;
+        if (!g_shell_parse_argv (command_applet->cmdline, NULL, &argv, &error)) {
+            gtk_label_set_text (command_applet->label, ERROR_OUTPUT);
+            g_clear_error (&error);
+            return G_SOURCE_CONTINUE;
+        }
+        g_strfreev(argv);
+        command_execute (command_applet);
+        return G_SOURCE_REMOVE;
+    }
 }
 
 static gboolean
 command_execute (CommandApplet *command_applet)
 {
-    GError *error = NULL;
-    gchar **argv;
-    gint stdout_fd;
-
-    /* command is empty, wait for next timer execution */
-    if (strlen (command_applet->command) == 0)
+    /* stop current timer */
+    if (command_applet->timeout_id != 0)
     {
-        return TRUE;
+        g_source_remove (command_applet->timeout_id);
+        command_applet->timeout_id = 0;
     }
 
-    /* command running, wait for next timer execution */
-    if (command_applet->child_pid != 0)
-    {
-        return TRUE;
+    if (command_applet->running) {
+        g_cancellable_cancel (command_applet->cancellable);
     }
 
-    if (!g_shell_parse_argv (command_applet->command, NULL, &argv, &error))
-    {
-        gtk_label_set_text (command_applet->label, ERROR_OUTPUT);
-        g_clear_error (&error);
-        return FALSE;
+    g_object_set (G_OBJECT(command_applet->command), "command", command_applet->cmdline, NULL);
+    ma_command_run_async (command_applet->command,
+                          command_applet->cancellable,
+                          command_async_ready_callback,
+                          command_applet);
+    if (!command_applet->running) {
+        command_applet->running = TRUE;
     }
 
-    if (!g_spawn_async_with_pipes (NULL,
-                                   argv,
-                                   NULL,
-                                   G_SPAWN_SEARCH_PATH | G_SPAWN_DO_NOT_REAP_CHILD,
-                                   NULL,
-                                   NULL,
-                                   &command_applet->child_pid,
-                                   NULL,
-                                   &stdout_fd,
-                                   NULL,
-                                   &error))
-    {
-        g_clear_error (&error);
-        g_strfreev (argv);
-        return TRUE;
+    if (g_cancellable_is_cancelled (command_applet->cancellable)) {
+        g_cancellable_reset (command_applet->cancellable);
     }
 
-    g_free(command_applet->buffer);
-    command_applet->buffer = g_new0(gchar, command_applet->width+1);
-
-    set_up_io_channel (stdout_fd, G_IO_IN|G_IO_PRI|G_IO_ERR|G_IO_HUP|G_IO_NVAL,
-                       stdout_io_func, command_applet);
-
-    if (command_applet->child_pid != (GPid) 0)
-        g_child_watch_add (command_applet->child_pid, on_child_exit, command_applet);
-
-    /* start timer for next execution */
     command_applet->timeout_id = g_timeout_add_seconds (command_applet->interval,
-                                                        (GSourceFunc) command_execute,
+                                                        (GSourceFunc) timeout_callback,
                                                         command_applet);
-    g_strfreev (argv);
-    return FALSE;
+    return G_SOURCE_CONTINUE;
 }
 
 static gboolean
@@ -434,15 +451,15 @@ command_applet_fill (MatePanelApplet* applet)
     command_applet->settings = mate_panel_applet_settings_new (applet, COMMAND_SCHEMA);
 
     command_applet->interval = g_settings_get_int (command_applet->settings, INTERVAL_KEY);
-    command_applet->command = g_settings_get_string (command_applet->settings, COMMAND_KEY);
+    command_applet->cmdline = g_settings_get_string (command_applet->settings, COMMAND_KEY);
     command_applet->width = g_settings_get_int (command_applet->settings, WIDTH_KEY);
+    command_applet->command = ma_command_new(command_applet->cmdline, NULL);
+    command_applet->cancellable = g_cancellable_new ();
 
     command_applet->box = GTK_BOX (gtk_box_new (GTK_ORIENTATION_HORIZONTAL, 0));
     command_applet->image = GTK_IMAGE (gtk_image_new_from_icon_name (APPLET_ICON, 24));
     command_applet->label = GTK_LABEL (gtk_label_new (ERROR_OUTPUT));
     command_applet->timeout_id = 0;
-    command_applet->child_pid = 0;
-    command_applet->buffer = NULL;
 
     /* we add the Gtk label into the applet */
     gtk_box_pack_start (command_applet->box,
@@ -489,7 +506,6 @@ command_applet_fill (MatePanelApplet* applet)
 
     /* first command execution */
     command_execute (command_applet);
-
     return TRUE;
 }
 
diff --git a/command/ma-command.c b/command/ma-command.c
new file mode 100644
index 00000000..da0e8795
--- /dev/null
+++ b/command/ma-command.c
@@ -0,0 +1,417 @@
+/*
+ * Copyright (C) 2018 Alberts Muktupāvels
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <config.h>
+#include "ma-command.h"
+
+#define BUFFER_SIZE 64
+
+struct _MaCommand
+{
+  GObject   parent;
+
+  gchar    *command;
+  gchar   **argv;
+};
+
+typedef struct
+{
+  GPid        pid;
+
+  GIOChannel *channel;
+
+  GString    *input;
+
+  guint       io_watch_id;
+  guint       child_watch_id;
+} CommandData;
+
+enum
+{
+  PROP_0,
+
+  PROP_COMMAND,
+
+  LAST_PROP
+};
+
+static GParamSpec *command_properties[LAST_PROP] = { NULL };
+
+static void initable_iface_init (GInitableIface *iface);
+
+G_DEFINE_TYPE_WITH_CODE (MaCommand, ma_command, G_TYPE_OBJECT,
+                         G_IMPLEMENT_INTERFACE (G_TYPE_INITABLE,
+                                                initable_iface_init))
+
+static gboolean
+read_cb (GIOChannel   *source,
+         GIOCondition  condition,
+         gpointer      user_data)
+{
+  GTask *task;
+  CommandData *data;
+  gchar buffer[BUFFER_SIZE];
+  gsize bytes_read;
+  GError *error;
+  GIOStatus status;
+
+  task = (GTask *) user_data;
+  data = g_task_get_task_data (task);
+
+  if (g_task_return_error_if_cancelled (task))
+    {
+      g_object_unref (task);
+
+      data->io_watch_id = 0;
+
+      return G_SOURCE_REMOVE;
+    }
+
+  error = NULL;
+  status = g_io_channel_read_chars (source, buffer, BUFFER_SIZE,
+                                    &bytes_read, &error);
+
+  if (status == G_IO_STATUS_AGAIN)
+    {
+      g_clear_error (&error);
+
+      return G_SOURCE_CONTINUE;
+    }
+  else if (status != G_IO_STATUS_NORMAL)
+    {
+      if (error != NULL)
+        {
+          g_task_return_error (task, error);
+          g_object_unref (task);
+        }
+
+      data->io_watch_id = 0;
+
+      return G_SOURCE_REMOVE;
+    }
+
+  g_string_append_len (data->input, buffer, bytes_read);
+
+  return G_SOURCE_CONTINUE;
+}
+
+static void
+child_watch_cb (GPid     pid,
+                gint     status,
+                gpointer user_data)
+{
+  GTask *task;
+  CommandData *data;
+
+  task = (GTask *) user_data;
+  data = g_task_get_task_data (task);
+
+  g_task_return_pointer (task, g_strdup (data->input->str), g_free);
+  g_object_unref (task);
+}
+
+static void
+cancelled_cb (GCancellable *cancellable,
+              gpointer      user_data)
+{
+  GTask *task;
+
+  task = G_TASK (user_data);
+
+  g_object_unref (task);
+}
+
+static void
+command_data_free (gpointer user_data)
+{
+  CommandData *data;
+
+  data = (CommandData *) user_data;
+
+  if (data->pid != 0)
+    {
+      g_spawn_close_pid (data->pid);
+      data->pid = 0;
+    }
+
+  if (data->channel != NULL)
+    {
+      g_io_channel_unref (data->channel);
+      data->channel = NULL;
+    }
+
+  if (data->input != NULL)
+    {
+      g_string_free (data->input, TRUE);
+      data->input = NULL;
+    }
+
+  if (data->io_watch_id != 0)
+    {
+      g_source_remove (data->io_watch_id);
+      data->io_watch_id = 0;
+    }
+
+  if (data->child_watch_id != 0)
+    {
+      g_source_remove (data->child_watch_id);
+      data->child_watch_id = 0;
+    }
+
+  g_free (data);
+}
+
+static gboolean
+ma_command_initable_init (GInitable     *initable,
+                          GCancellable  *cancellable,
+                          GError       **error)
+{
+  MaCommand *command;
+
+  command = MA_COMMAND (initable);
+
+  if (command->command == NULL || *command->command == '\0')
+    {
+      g_set_error (error, G_IO_ERROR, G_IO_ERROR_INVALID_DATA,
+                   "Empty command");
+
+      return FALSE;
+    }
+
+  return TRUE;
+}
+
+static void
+initable_iface_init (GInitableIface *iface)
+{
+  iface->init = ma_command_initable_init;
+}
+
+static void
+ma_command_finalize (GObject *object)
+{
+  MaCommand *command;
+
+  command = MA_COMMAND (object);
+
+  g_clear_pointer (&command->command, g_free);
+  g_clear_pointer (&command->argv, g_strfreev);
+
+  G_OBJECT_CLASS (ma_command_parent_class)->finalize (object);
+}
+
+static void
+ma_command_set_property (GObject      *object,
+                         guint         property_id,
+                         const GValue *value,
+                         GParamSpec   *pspec)
+{
+  MaCommand *command;
+
+  command = MA_COMMAND (object);
+
+  switch (property_id)
+    {
+      case PROP_COMMAND:
+          //g_assert (command->command == NULL);
+          command->command = g_value_dup_string (value);
+          if (command->argv && *command->argv != NULL) {
+              g_strfreev(command->argv);
+          }
+          g_shell_parse_argv (command->command, NULL, &command->argv, NULL);
+        break;
+
+      default:
+        G_OBJECT_WARN_INVALID_PROPERTY_ID (object, property_id, pspec);
+        break;
+    }
+}
+
+static void
+ma_command_get_property (GObject *object, guint prop_id, GValue *value, GParamSpec *pspec)
+{
+    MaCommand *command;
+
+    command = MA_COMMAND (object);
+
+    switch (prop_id)
+    {
+        case PROP_COMMAND:
+            g_value_set_string (value, command->command);
+        default:
+            G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
+            break;
+    }
+}
+
+static void
+install_properties (GObjectClass *object_class)
+{
+  command_properties[PROP_COMMAND] =
+    g_param_spec_string ("command", "command", "command",
+                         NULL,
+                         G_PARAM_READWRITE);
+
+  g_object_class_install_properties (object_class, LAST_PROP,
+                                     command_properties);
+}
+
+static void
+ma_command_class_init (MaCommandClass *command_class)
+{
+  GObjectClass *object_class;
+
+  object_class = G_OBJECT_CLASS (command_class);
+
+  object_class->finalize = ma_command_finalize;
+  object_class->set_property = ma_command_set_property;
+  object_class->get_property = ma_command_get_property;
+
+  install_properties (object_class);
+}
+
+static void
+ma_command_init (MaCommand *command)
+{
+}
+
+/**
+ * ma_command_new:
+ * @command: a command
+ * @error: (nullable): return location for an error, or %NULL
+ *
+ * Creates a new #MaCommand.
+ *
+ * Returns: (nullable): a newly allocated #MaCommand
+ */
+MaCommand *
+ma_command_new (const gchar  *command,
+                GError      **error)
+{
+  return g_initable_new (MA_TYPE_COMMAND, NULL, error,
+                         "command", command,
+                         NULL);
+}
+
+/**
+ * ma_command_run_async:
+ * @command: a #MaCommand
+ * @cancellable: (nullable): a #GCancellable or %NULL
+ * @callback: a #GAsyncReadyCallback to call when the request is satisfied
+ * @user_data: the data to pass to @callback
+ *
+ * Request an asynchronous read of output from command that was passed
+ * to ma_command_new().
+ */
+void
+ma_command_run_async (MaCommand           *command,
+                      GCancellable        *cancellable,
+                      GAsyncReadyCallback  callback,
+                      gpointer             user_data)
+{
+  GTask *task;
+  CommandData *data;
+  GSpawnFlags spawn_flags;
+  gint command_stdout;
+  GError *error;
+  GIOChannel *channel;
+  GIOStatus status;
+  GIOCondition condition;
+
+  g_return_if_fail (MA_IS_COMMAND (command));
+  g_return_if_fail (callback != NULL);
+
+  task = g_task_new (command, cancellable, callback, user_data);
+  g_task_set_source_tag (task, ma_command_run_async);
+
+  if (cancellable)
+    {
+      g_signal_connect_object (cancellable, "cancelled",
+                               G_CALLBACK (cancelled_cb), task,
+                               G_CONNECT_AFTER);
+    }
+
+  data = g_new0 (CommandData, 1);
+  g_task_set_task_data (task, data, command_data_free);
+
+  spawn_flags = G_SPAWN_SEARCH_PATH | G_SPAWN_DO_NOT_REAP_CHILD;
+  error = NULL;
+
+  if (!g_spawn_async_with_pipes (NULL, command->argv, NULL, spawn_flags,
+                                 NULL, NULL, &data->pid, NULL, &command_stdout,
+                                 NULL, &error))
+    {
+      g_task_return_error (task, error);
+      g_object_unref (task);
+
+      return;
+    }
+
+  channel = data->channel = g_io_channel_unix_new (command_stdout);
+  g_io_channel_set_close_on_unref (channel, TRUE);
+
+  g_assert (error == NULL);
+  status = g_io_channel_set_encoding (channel, NULL, &error);
+
+  if (status != G_IO_STATUS_NORMAL)
+    {
+      g_task_return_error (task, error);
+      g_object_unref (task);
+
+      return;
+    }
+
+  g_assert (error == NULL);
+  status = g_io_channel_set_flags (channel, G_IO_FLAG_NONBLOCK, &error);
+
+  if (status != G_IO_STATUS_NORMAL)
+    {
+      g_task_return_error (task, error);
+      g_object_unref (task);
+
+      return;
+    }
+
+  data->input = g_string_new (NULL);
+
+  condition = G_IO_IN | G_IO_PRI | G_IO_ERR | G_IO_HUP;
+  data->io_watch_id = g_io_add_watch (channel, condition, read_cb, task);
+
+  data->child_watch_id = g_child_watch_add (data->pid, child_watch_cb, task);
+}
+
+/**
+ * ma_command_run_finish:
+ * @command: a #MaCommand
+ * @result: a #GAsyncResult
+ * @error: (nullable): return location for an error, or %NULL
+ *
+ * Finishes an operation started with ma_command_run_async().
+ *
+ * Returns: %NULL if @error is set, otherwise output from command
+ */
+gchar *
+ma_command_run_finish (MaCommand     *command,
+                       GAsyncResult  *result,
+                       GError       **error)
+{
+  g_return_val_if_fail (MA_IS_COMMAND (command), NULL);
+  g_return_val_if_fail (g_task_is_valid (result, command), NULL);
+  g_return_val_if_fail (error == NULL || *error == NULL, NULL);
+
+  return g_task_propagate_pointer (G_TASK (result), error);
+}
diff --git a/command/ma-command.h b/command/ma-command.h
new file mode 100644
index 00000000..8fb51ab3
--- /dev/null
+++ b/command/ma-command.h
@@ -0,0 +1,43 @@
+/*
+ * Copyright (C) 2018 Alberts Muktupāvels
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef MA_COMMAND_H
+#define MA_COMMAND_H
+
+#include <gio/gio.h>
+#include <glib-object.h>
+
+G_BEGIN_DECLS
+
+#define MA_TYPE_COMMAND (ma_command_get_type ())
+G_DECLARE_FINAL_TYPE (MaCommand, ma_command, MA, COMMAND, GObject)
+
+MaCommand *ma_command_new        (const gchar          *command,
+                                  GError              **error);
+
+void       ma_command_run_async  (MaCommand            *command,
+                                  GCancellable         *cancellable,
+                                  GAsyncReadyCallback   callback,
+                                  gpointer              user_data);
+
+gchar     *ma_command_run_finish (MaCommand            *command,
+                                  GAsyncResult         *result,
+                                  GError              **error);
+
+G_END_DECLS
+
+#endif