diff --git a/spawn.lua b/spawn.lua
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+++ b/spawn.lua
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+-- spawn.lua - wrapper around Awesome awful.spawn with fallback
+-- Copyright (C) 2019  Nguyễn Gia Phong
+--
+-- This file is part of Vicious.
+--
+-- Vicious 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.
+--
+-- Vicious 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 Affero General Public License for more details.
+--
+-- You should have received a copy of the GNU Affero General Public License
+-- along with Vicious.  If not, see <https://www.gnu.org/licenses/>.
+
+local status, spawn = pcall(require, "awful.spawn")
+if status then return spawn end
+
+local io = { popen = io.popen }
+
+-- In case the Awesome library is not available,
+-- fall back to this synchronous, handicapped API.
+local spawn = {}
+
+--- Spawn a program and capture its output line by line.
+-- @tparam string|table cmd The command.
+-- @tab callbacks Table containing callbacks that should be invoked on
+--   various conditions.
+-- @tparam[opt] function callbacks.stdout Function that is called with each
+--   line of output on stdout, e.g. `stdout(line)`.
+-- @tparam[opt] function callbacks.stderr Function that is supposed to be called
+--   with each line of output on stderr, but due to limitation of io.popen,
+--   stderr will be discarded (sorry!).
+-- @tparam[opt] function callbacks.output_done Function to call when no more
+--   output is produced.
+-- @tparam[opt] function callbacks.exit Function to call when the spawned
+--   process exits. This function gets the exit reason and code as its
+--   arguments.
+--   The reason can be "exit" or "signal".
+--   For "exit", the second argument is the exit code.
+--   For "signal", the second argument is the signal causing process
+--   termination.
+-- @treturn boolean|nil true if cmd terminated successfully, or nil otherwise
+function spawn.with_line_callback(cmd, callbacks)
+    local stdout_callback, stdout = callbacks.stdout, io.popen(cmd)
+    for line in stdout:lines() do stdout_callback(line) end
+    if callbacks.output_done then callbacks.output_done() end
+
+    local success, reason, code = stdout:close()    -- this requires Lua 5.2
+    if callbacks.exit then callbacks.exit(reason, code) end
+    return success
+end
+
+--- Spawn a program and capture its output.
+-- @tparam string|table cmd The command.
+-- @tab callback Function with the following arguments
+--   @tparam string callback.stdout Output on stdout.
+--   @tparam string callback.stderr Output on stderr,
+--     which will be an empty due to limitation of io.popen.
+--   @tparam string callback.exitreason Exit reason ("exit" or "signal").
+--   @tparam integer callback.exitcode Exit code (exit code or signal number,
+--     depending on "exitreason").
+-- @treturn boolean|nil true if cmd terminated successfully, or nil otherwise
+function spawn.easy_async(cmd, callback)
+    local out_stream = io.popen(cmd)
+    local stdout = out_stream:read("*all")
+    local success, reason, code = out_stream:close()    -- requiring Lua 5.2
+    callback(stdout, "", reason, code)
+    return success
+end
+
+return spawn
+-- vim: filetype=lua:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:textwidth=80