Module: `awful.spawn`

Spawn sub-processes and optionally get their output.

This module provides methods to start programs and supports startup notifications, which allows for callbacks and applying properties to the program after it has been launched. This requires currently that the application supports them.

Frequently asked questions

Rules of thumb when a shell is needed:

A shell is required when the commands contain &&, ;, ||, & or any other unix shell language syntax
When shell variables are defined as part of the command
When the command is a shell alias

Note that a shell is not a terminal emulator. A terminal emulator is something like XTerm, Gnome-terminal or Konsole. A shell is something like bash, zsh, busybox sh or Debian ash.

If you wish to open a process in a terminal window, check that your terminal emulator supports the common -e option. If it does, then something like this should work:

awful.spawn(terminal.." -e my_command")

Note that some terminals, such as rxvt-unicode (urxvt) support full commands using quotes, while other terminal emulators require to use quoting.

Understanding clients versus PID versus commands versus class:

A process has a PID (process identifier). It can have 0, 1 or many windows.

A command is what is used to start process(es). It has no direct relation with process, client or window. When a command is executed, it will usually start a process which keeps running until it exits. This however is not always the case as some applications use scripts as command and others use various single-instance mechanisms (usually client/server) and merge with an existing process.

A client corresponds to a window. It is owned by a process. It can have both a parent and one or many children. A client has a class, an instance, a role, and a type. See client.class, client.instance, client.role and client.type for more information about these properties.

Understanding blocking versus asynchronous execution:

Awesome is single threaded, it means only one thing is executed at any time. But Awesome isn't doomed to be slow. It may not have multiple threads, but it has something called coroutine and also has callbacks. This means things that take time to execute can still do so in the background (using C threads or external process + sockets). When they are done, they can notify the Awesome thread. This works perfectly and avoid blocking Awesome.

If you want to update the text of a wibox.widget.textbox with the output of a shell command, you should use the awful.spawn.easy_async_with_shell command. It is strongly recommended not to use io.popen is explained in the "Getting a command's output" section. Asynchronous execution is at first a bit tricky to understand if you never used that before. The example below should demonstrate how it works.

If we do (but really, don't do that):

-- **NEVER, EVER, DO THIS**: your computer will freeze
os.execute("sleep 1; echo foo > /tmp/foo.txt")
mylabel.text = io.popen("cat /tmp/foo.txt"):read("*all")

The label will display foo. But If we do:

-- Don't do this, it won't work.
-- Assumes /tmp/foo.txt does not exist
awful.spawn.with_shell("sleep 1; echo foo > /tmp/foo.txt")
mylabel.text = io.popen("cat /tmp/foo.txt"):read("*all")

Then the label will be empty. awful.spawn and awful.spawn.with_shell will not block and thus the io.popen will be executed before sleep 1 finishes. This is why we have async functions to execute shell commands. There are many variants with difference characteristics and complexity. awful.spawn.easy_async is the most common as it is good enough for the general "I want to execute a command and do something with the output when it finishes".

-- This is the correct way
local command = "sleep 1; echo foo > /tmp/foo.txt"

awful.spawn.easy_async_with_shell(command, function()
    awful.spawn.easy_async_with_shell("cat /tmp/foo.txt", function(out)
        mylabel.text = out
    end)
end)

In this variant, Awesome will not block. Again, like other spawn, you cannot add code outside of the callback function to use the result of the command. The code will be executed before the command is finished so the result won't yet be available.

Getting a command's output:

First, do not use io.popen ever. It is synchronous. Synchronous functions block everything until they are done. All visual applications lock (as Awesome no longer responds), you will probably lose some keyboard and mouse events and will have higher latency when playing games. This is also true when reading files synchronously, but this is another topic.

Awesome provides a few ways to get output from commands. One is to use the Gio libraries directly. This is usually very complicated, but gives a lot of control on the command execution.

This modules provides with_line_callback and easy_async for convenience. First, lets add this bash command to rc.lua:

local noisy = [[bash -c '
  for I in $(seq 1 5); do
    date
    echo err >&2
    sleep 2
  done
']]

It prints a bunch of junk on the standard output (stdout) and error (stderr) streams. This command would block Awesome for 10 seconds if it were executed synchronously, but will not block it at all using the asynchronous functions.

with_line_callback will execute the callbacks every time a new line is printed by the command:

awful.spawn.with_line_callback(noisy, {
    stdout = function(line)
        naughty.notification { message = "LINE:"..line }
    end,
    stderr = function(line)
        naughty.notification { message = "ERR:"..line}
    end,
})

If only the full output is needed, then easy_async is the right choice:

awful.spawn.easy_async(noisy, function(stdout, stderr, reason, exit_code)
    naughty.notification { message = stdout }
end)

Default applications:

If the intent is to open a file/document, then it is recommended to use the following standard command. The default application will be selected according to the Shared MIME-info Database specification. The xdg-utils package provided by most distributions includes the xdg-open command:

awful.spawn({"xdg-open", "/path/to/file"})

Awesome does not manage, modify or otherwise influence the database for default applications. For information about how to do this, consult the ARCH Linux Wiki.

If you wish to change how the default applications behave, then consult the Desktop Entry specification.

Spawning applications with specific properties

The startup notification protocol:

The startup notification protocol is an optional specification implemented by X11 applications to bridge the chain of knowledge between the moment a program is launched to the moment its window (client) is shown. It can be found on the FreeDesktop.org website.

Awesome has support for the various events that are part of the protocol, but the most useful is the identifier, usually identified by its SNID acronym in the documentation. It isn't usually necessary to even know it exists, as it is all done automatically. However, if more control is required, the identifier can be specified by an environment variable called DESKTOP_STARTUP_ID. For example, let us consider execution of the following command:

DESKTOP_STARTUP_ID="something_TIME$(date '+%s')" my_command

This should (if the program correctly implements the protocol) result in c.startup_id to at least match something. This identifier can then be used in ruled.client to configure the client.

Awesome can automatically set the DESKTOP_STARTUP_ID variable. This is used by awful.spawn to specify additional rules for the startup. For example:

awful.spawn("urxvt -e maxima -name CALCULATOR", {
    floating  = true,
    tag       = mouse.screen.selected_tag,
    placement = awful.placement.bottom_right,
})

This can also be used from the command line:

awesome-client 'awful=require("awful");
  awful.spawn("urxvt -e maxima -name CALCULATOR", {
    floating  = true,
    tag       = mouse.screen.selected_tag,
    placement = awful.placement.bottom_right,
  })'

This table contains the client properties that are valid when used the sn_rules or prop function argument. They are the same as in ruled.client.

Name	Description
placement	The client default placement on the screen
honor\_padding	When applying the placement, honor the screen padding
honor\_workarea	When applying the placement, honor the screen work area
tag	The client default tag
tags	The client default tags
new\_tag	Create a new tag for this client
switch\_to\_tags	Unselect the current tags and select this client tags
focus	Define if the client should grab focus by default
titlebars\_enabled	Should this client have a titlebar by default
callback	A function to call when this client is ready
marked	If a client is marked or not
is\_fixed	Return if a client has a fixed size or not
immobilized\_horizontal	Is the client immobilized horizontally?
immobilized\_vertical	Is the client immobilized vertically?
floating	The client floating state
x	The x coordinates
y	The y coordinates
width	The width of the client
height	The height of the client
dockable	If the client is dockable
requests\_no\_titlebar	If the client requests not to be decorated with a titlebar
shape	Set the client shape
active	Return true if the client is active (has focus)
window	The X window id
name	The client title
skip\_taskbar	True if the client does not want to be in taskbar
type	The window type
class	The client class
instance	The client instance
pid	The client PID, if available
role	The window role, if available
machine	The machine client is running on
icon\_name	The client name when iconified
icon	The client icon as a surface
icon\_sizes	The available sizes of client icons
screen	Client screen
hidden	Define if the client must be hidden, i
minimized	Define it the client must be iconify, i
size\_hints\_honor	Honor size hints, e
border\_width	The client border width
border\_color	The client border color
urgent	The client urgent state
content	A cairo surface for the client window content
opacity	The client opacity
ontop	The client is on top of every other windows
above	The client is above normal windows
below	The client is below normal windows
fullscreen	The client is fullscreen or not
maximized	The client is maximized (horizontally and vertically) or not
maximized\_horizontal	The client is maximized horizontally or not
maximized\_vertical	The client is maximized vertically or not
transient\_for	The client the window is transient for
group\_window	Window identification unique to a group of windows
leader\_window	Identification unique to windows spawned by the same command
size\_hints	A table with size hints of the client
motif\_wm\_hints	The motif WM hints of the client
sticky	Set the client sticky, i
modal	Indicate if the client is modal
focusable	True if the client can receive the input focus
shape\_bounding	The client's bounding shape as set by awesome as a (native) cairo surface
shape\_clip	The client's clip shape as set by awesome as a (native) cairo surface
shape\_input	The client's input shape as set by awesome as a (native) cairo surface
client\_shape\_bounding	The client's bounding shape as set by the program as a (native) cairo surface
client\_shape\_clip	The client's clip shape as set by the program as a (native) cairo surface
startup\_id	The FreeDesktop StartId
valid	If the client that this object refers to is still managed by awesome
first\_tag	The first tag of the client
buttons	Get or set mouse buttons bindings for a client
keys	Get or set keys bindings for a client

Info:

Copyright: 2008 Julien Danjou,2014 Emmanuel Lepage Vallee
Originally authored by: Julien Danjou <[email protected]>,Emmanuel Lepage Vallee <[email protected]>
(Full contributors list available on our github project)

Static module functions

awful.spawn (cmd, sn_rules, callback) -> (integer, nil or string) or string	Spawn a program, and optionally apply properties and/or run a callback.
awful.spawn.with_shell (cmd) -> (integer, nil or string) or string	Spawn a program using the shell.
awful.spawn.with_line_callback (cmd, callbacks) -> Integer or string	Spawn a program and asynchronously capture its output line by line.
awful.spawn.easy_async (cmd, callback) -> Integer or string	Asynchronously spawn a program and capture its output.
awful.spawn.easy_async_with_shell (cmd, callback) -> Integer or string	Call spawn.easy_async with a shell.
awful.spawn.read_lines (input_stream, line_callback, done_callback, close)	Read lines from a Gio input stream
awful.spawn.once (cmd, rules, matcher, unique_id, callback)	Spawn a command if it has not been spawned before.
awful.spawn.single_instance (cmd, rules, matcher, unique_id, callback)	Spawn a command if an instance is not already running.
awful.spawn.raise_or_spawn (cmd, rules, matcher, unique_id, callback) -> client	Raise a client if it exists or spawn a new one then raise it.

Static module functions

🔗 awful.spawn (cmd, sn_rules, callback) -> (integer, nil or string) or string

Spawn a program, and optionally apply properties and/or run a callback.

Applying properties or running a callback requires the program/client to support startup notifications.

See ruled.client.execute for more details about the format of sn_rules.

Parameters:

Name		Type(s)	Description	Default value
cmd		string or table	The command.	Not applicable
sn_rules	Optional	table or boolean	A table of properties to be applied after startup; `false` to disable startup notifications.	`true`
callback	Optional	function	A callback function to be run after startup.	Undefined

Returns:

integer The forked PID.
optional string The startup notification ID, if sn is not false, or a callback is provided.

Or

string

🔗 awful.spawn.with_shell (cmd) -> (integer, nil or string) or string

Spawn a program using the shell. This calls cmd with $SHELL -c (via awful.util.shell).

Parameters:

Name		Type(s)	Description
cmd		string	The command.

Returns:

integer The forked PID.
optional string The startup notification ID, if sn is not false, or a callback is provided.

Or

string

🔗 awful.spawn.with_line_callback (cmd, callbacks) -> Integer or string

Spawn a program and asynchronously capture its output line by line.

Parameters:

Name		Type(s)	Description
cmd		string or table	The command.
callbacks		table	Table containing callbacks that should be invoked on various conditions.
stdout	Optional	function	Function that is called with each line of output on stdout, e.g. `stdout(line)`.
stderr	Optional	function	Function that is called with each line of output on stderr, e.g. `stderr(line)`.
output_done	Optional	function	Function to call when no more output is produced.
exit	Optional	function	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.

Returns:

Integer

Or

string

🔗 awful.spawn.easy_async (cmd, callback) -> Integer or string

Asynchronously spawn a program and capture its output. (wraps spawn.with_line_callback).

Parameters:

Name	Type(s)	Description
cmd	string or table	The command.
callback	table	Function with the following arguments
stdout	string	Output on stdout.
stderr	string	Output on stderr.
exitreason	string	Exit reason ("exit" or "signal").
exitcode	integer	Exit code (exit code or signal number, depending on `exitreason`).

Returns:

Integer

Or

string

Parameters:

Name	Type(s)	Description
cmd	string	The command.
callback	table	Function with the following arguments
stdout	string	Output on stdout.
stderr	string	Output on stderr.
exitreason	string	Exit reason ("exit" or "signal").
exitcode	integer	Exit code (exit code or signal number, depending on `exitreason`).

Returns:

Integer

Or

string

Parameters:

Name		Type(s)	Description	Default value
input_stream		Gio.InputStream	The input stream to read from.	Not applicable
line_callback		function	Function that is called with each line read, e.g. `line_callback(line_from_stream)`.	Not applicable
done_callback	Optional	function	Function that is called when the operation finishes (e.g. due to end of file).	Undefined
close	Optional	boolean	Should the stream be closed after end-of-file?	`false`

🔗 awful.spawn.once (cmd, rules, matcher, unique_id, callback)

Spawn a command if it has not been spawned before.

This function tries its best to preserve the state across awesome.restart().

By default, when no unique_id is specified, this function will generate one by hashing the command and its rules. If you have multiple instance of the same command and rules, you need to specify an UID or only the first one will be executed.

The rules are standard ruled.client.

This function depends on the startup notification protocol to be correctly implemented by the command. See client.startup_id for more information. Note that this also won't work with shell or terminal commands.

Parameters:

Name		Type(s)	Description
cmd		string or table	The command.
rules	Optional	table	The properties that need to be applied to the client.
matcher	Optional	function	A matching function to find the instance among running clients.
unique_id	Optional	string	A string to identify the client so it isn't executed multiple time.
callback	Optional	function	A callback function when the client is created.

Parameters:

Name		Type(s)	Description
cmd		string or table	The command.
rules	Optional	table	The properties that need to be applied to the client.
matcher	Optional	function	A matching function to find the instance among running clients.
unique_id	Optional	string	A string to identify the client so it isn't executed multiple time.
callback	Optional	function	A callback function when the client is created.

Parameters:

Name		Type(s)	Description
cmd		string or table	The command.
rules		table	The properties that need to be applied to the client.
matcher	Optional	function	A matching function to find the instance among running clients.
unique_id	Optional	string	A string to identify the client so it isn't executed multiple time.
callback	Optional	function	A callback function when the client is created.

Returns:

client

Requested actions or permissions:

Class	Permission	Context	Default	Description
client	activate	spawn.raise_or_spawn	granted	Activate a client when awful.spawn.raise_or_spawn is called and the client exists.

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Documentation

Module: awful.spawn

Frequently asked questions

Spawning applications with specific properties

Info:

Static module functions

Static module functions

Parameters:

Returns:

Or

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See also:

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Requested actions or permissions:

Module: `awful.spawn`