docs » hs.task

Execute processes in the background and capture their output

Notes:

API Overview

API Documentation

Functions

new
Signature hs.task.new(launchPath, callbackFn[, streamCallbackFn, arguments]) -> hs.task object
Type Function
Description

Creates a new hs.task object

Parameters:

  • launchPath - A string containing the path to an executable file. This must be the full path to an executable and not just an executable which is in your environment's path (e.g. /bin/ls rather than just ls).
  • callbackFn - A callback function to be called when the task terminates, or nil if no callback should be called. The function should accept three arguments:
    • exitCode - An integer containing the exit code of the process
    • stdOut - A string containing the standard output of the process
    • stdErr - A string containing the standard error output of the process
  • streamCallbackFn - A optional callback function to be called whenever the task outputs data to stdout or stderr. The function must return a boolean value - true to continue calling the streaming callback, false to stop calling it. The function should accept three arguments:
    • task - The hs.task object
    • stdOut - A string containing the standard output received since the last call to this callback
    • stdErr - A string containing the standard error output received since the last call to this callback
  • arguments - An optional table containing command line arguments for the executable

Returns:

  • An hs.task object

Notes:

  • The arguments are not processed via a shell, so you do not need to do any quoting or escaping. They are passed to the executable exactly as provided.

Methods

closeInput
Signature hs.task:closeInput() -> hs.task object
Type Method
Description

Closes the task's stdin

Parameters:

  • None

Returns:

  • The hs.task object

Notes:

  • This should only be called on tasks with a streaming callback - tasks without it will automatically close stdin when any data supplied via hs.task:setInput() has been written
  • This is primarily useful for sending EOF to long-running tasks
environment
Signature hs.task:environment() -> environment
Type Method
Description

Returns the environment variables as a table for the task.

Parameters:

  • None

Returns:

  • a table of the environment variables for the task where each key is the environment variable name.

Note:

  • if you have not yet set an environment table with the hs.task:setEnvironment method, this method will return a copy of the Hammerspoon environment table, as this is what the task will inherit by default.
interrupt
Signature hs.task:interrupt() -> hs.task object
Type Method
Description

Interrupts the task

Parameters:

  • None

Returns:

  • The hs.task object

Notes:

  • This will send SIGINT to the process
isRunning
Signature hs.task:isRunning() -> boolean
Type Method
Description

Test if a task is still running.

Parameters:

  • None

Returns:

  • true if the task is running or false if it is not.

Notes:

  • A task which has not yet been started yet will also return false.
pause
Signature hs.task:pause() -> boolean
Type Method
Description

Pauses the task

Parameters:

  • None

Returns:

  • If the task was paused successfully, returns the task object; otherwise returns false

Notes:

  • If the task is not paused, the error message will be printed to the Hammerspoon Console
  • This method can be called multiple times, but a matching number of hs.task:resume() calls will be required to allow the process to continue
pid
Signature hs.task:pid() -> integer
Type Method
Description

Gets the PID of a running/finished task

Parameters:

  • None

Returns:

  • An integer containing the PID of the task

Notes:

  • The PID will still be returned if the task has already completed and the process terminated
resume
Signature hs.task:resume() -> boolean
Type Method
Description

Resumes the task

Parameters:

  • None

Returns:

  • If the task was resumed successfully, returns the task object; otherwise returns false

Notes:

  • If the task is not resumed successfully, the error message will be printed to the Hammerspoon Console
setCallback
Signature hs.task:setCallback(fn) -> hs.task object
Type Method
Description

Set or remove a callback function for a task.

Parameters:

  • fn - A function to be called when the task completes or is terminated, or nil to remove an existing callback

Returns:

  • the hs.task object
setEnvironment
Signature hs.task:setEnvironment(environment) -> hs.task object | false
Type Method
Description

Sets the environment variables for the task.

Parameters:

  • environment - a table of key-value pairs representing the environment variables that will be set for the task.

Returns:

  • The hs.task object, or false if the table was not set (usually because the task is already running or has completed)

Note:

  • If you do not set an environment table with this method, the task will inherit the environment variables of the Hammerspoon application. Set this to an empty table if you wish for no variables to be set for the task.
setInput
Signature hs.task:setInput(inputData) -> hs.task object
Type Method
Description

Sets the standard input data for a task

Parameters:

  • inputData - Data, in string form, to pass to the task as its standard input

Returns:

  • The hs.task object

Notes:

  • This method can be called before the task has been started, to prepare some input for it (particularly if it is not a streaming task)
  • If this method is called multiple times, any input that has not been passed to the task already, is discarded (for streaming tasks, the data is generally consumed very quickly, but for now there is no way to syncronise this)
setStreamingCallback
Signature hs.task:setStreamingCallback(fn) -> hs.task object
Type Method
Description

Set a stream callback function for a task

Parameters:

  • fn - A function to be called when the task outputs to stdout or stderr, or nil to remove a callback

Returns:

  • The hs.task object

Notes:

  • For information about the requirements of the callback function, see hs.task.new()
  • If a callback is removed without it previously having returned false, any further stdout/stderr output from the task will be silently discarded
setWorkingDirectory
Signature hs.task:setWorkingDirectory(path) -> hs.task object | false
Type Method
Description

Sets the working directory for the task.

Parameters:

  • path - a string containing the path you wish to be the working directory for the task.

Returns:

  • The hs.task object, or false if the working directory was not set (usually because the task is already running or has completed)

Notes:

  • You can only set the working directory if the task has not already been started.
  • This will only set the directory that the task starts in. The task itself can change the directory while it is running.
start
Signature hs.task:start() -> hs.task object | false
Type Method
Description

Starts the task

Parameters:

  • None

Returns:

  • If the task was started successfully, returns the task object; otherwise returns false

Notes:

  • If the task does not start successfully, the error message will be printed to the Hammerspoon Console
terminate
Signature hs.task:terminate() -> hs.task object
Type Method
Description

Terminates the task

Parameters:

  • None

Returns:

  • The hs.task object

Notes:

  • This will send SIGTERM to the process
terminationReason
Signature hs.task:terminationReason() -> exitCode | false
Type Method
Description

Returns the termination reason for a task, or false if the task is still running.

Parameters:

  • None

Returns:

  • a string value of "exit" if the process exited normally or "interrupt" if it was killed by a signal. Returns false if the termination reason is unavailable (the task is still running, or has not yet been started).
terminationStatus
Signature hs.task:terminationStatus() -> exitCode | false
Type Method
Description

Returns the termination status of a task, or false if the task is still running.

Parameters:

  • None

Returns:

  • the numeric exitCode of the task, or the boolean false if the task has not yet exited (either because it has not yet been started or because it is still running).
waitUntilExit
Signature hs.task:waitUntilExit() -> hs.task object
Type Method
Description

Blocks Hammerspoon until the task exits

Parameters:

  • None

Returns:

  • The hs.task object

Notes:

  • All Lua and Hammerspoon activity will be blocked by this method. Its use is highly discouraged.
workingDirectory
Signature hs.task:workingDirectory() -> path
Type Method
Description

Returns the working directory for the task.

Parameters:

  • None

Returns:

  • a string containing the working directory for the task.

Notes:

  • This only returns the directory that the task starts in. If the task changes the directory itself, this value will not reflect that change.