Termux:Tasker

A Termux add-on app allowing Termux commands to be executed from Tasker and other plugin apps.

Contents

• Installation
• Setup Instructions
• Usage
• Plugin Configuration
• Plugin Variables
• Templates
• Creating And Modifying Scripts
• Debugging
• Worthy Of Note
• License

Installation

Termux:Tasker application can be obtained from F-Droid.

Additionally we provide per-commit debug builds for those who want to try out the latest features or test their pull request. This build can be obtained from one of the workflow runs listed on Github Actions page.

The APK files in F-Droid releases or Github Actions builds are signed with different signature keys. The Termux app and all its plugins use the same sharedUserId com.termux and so all their APKs installed on a device must have been signed with the same signature key to work together and so they must all be installed from the same source. Do not attempt to mix them together, i.e do not try to install an app or plugin from F-Droid and another from different source. Android Package Manager will also normally not allow installation of APKs with a different signatures and you will get an error on installation but this restriction can be bypassed with root or with custom roms. If you wish to install from a different source, then you must uninstall any and all existing Termux app or its plugin APKs from your device first, then install all new APKs from the same new source again. The ~/.termux/tasker/ directory will not be accessible to the plugin and commands will not execute if Termux and Termux:Tasker APKs have a different signatures.

Setup Instructions

Install Termux app (Mandatory)

The Termux:Tasker plugin requires Termux app to run the actual commands. You need to install it and start it at least once and have it install the required files for the plugin to start working. The Termux prefix directory /data/data/com.termux/files/usr/ and Termux home directory /data/data/com.termux/files/home/ must also exist and must have read, write and execute permissions (0700) for the plugin to work. The $PREFIX/ is shortcut for the Termux prefix directory. The ~/ is a shortcut for the Termux home directory. Permissions and ownerships can be checked with the stat <path> command.

com.termux.permission.RUN_COMMAND permission (Mandatory)

For Termux:Tasker version >= 0.5, the plugin host app will need to be granted the com.termux.permission.RUN_COMMAND permission to run ANY plugin commands. This is a security measure to prevent any other apps from running commands in Termux context which do not have the required permission granted to them. This is also required for the RUN_COMMAND Intent intent.

The Tasker app has requested the permission since v5.9.3, so you will need to update the app if you are using an older version. You can grant the permission using the Permissions activity in the App Info activity of your plugin host app. For Tasker you can grant it with: Android Settings -> Apps -> Tasker -> Permissions -> Additional permissions -> Run commands in Termux environment.

If you do not grant the permission, you will likely get errors like receiver com.termux.tasker.FireReceiver requires permission com.termux.permission.RUN_COMMAND which we don't have when running the Termux:Tasker plugin action in Tasker. Note that, the %errmsg for missing permissions will not be set if you are using Tasker version < 5.11.1.beta and Continue Task After Error is enabled, only %err will be set to 1. You can open the plugin configuration screen to detect missing permissions of the plugin host.

~/.termux/tasker/ Directory (Optional)

The ~/.termux/tasker/ directory stores the scripts that can be run with the plugin without setting allow-external-apps property to true if you do not want to use absolute paths. Open a non-root termux session and run the below command to create it and give it read, write and executable permissions (0700). The tasker directory must have read permission, otherwise the plugin will not be able to read the script files and give errors like No regular file found at path for any script name entered in the Executable field of plugin configuration. The tasker directory of the script must also have executable permissions for the script to be allowed to execute.

mkdir -p /data/data/com.termux/files/home/.termux/tasker
chmod 700 -R /data/data/com.termux/files/home/.termux

allow-external-apps property (Optional)

Termux:Tasker version >= 0.5 also allows commands to be run outside the ~/.termux/tasker/ directory by setting absolute paths in the Executable field of the plugin configuration ONLY if allow-external-apps property is set to true in ~/.termux/termux.properties file. This is an added security measure. DO NOT set it to true if you have given a relatively untrusted app com.termux.permission.RUN_COMMAND permission, since it will be able to run arbitrary commands in termux or even root context (assuming termux has been granted root permissions) in the background without user intervention. The ~/.termux directory must have read permission, otherwise the plugin will not be able to read the property values. This is also required for the RUN_COMMAND Intent intent.

• Automatic You can use the one-liner commands below to set the desired value. The commands will append the desired value using echo command to the file if the file doesn't exist or the property doesn't exist in the file, otherwise it will sed replace any existing values of the key with the desired value.

  To set allow-external-apps property to true.

    value="true"; key="allow-external-apps"; file="/data/data/com.termux/files/home/.termux/termux.properties"; mkdir -p "$(dirname "$file")"; chmod 700 "$(dirname "$file")"; if ! grep -E '^'"$key"'=.*' $file &>/dev/null; then [[ -s "$file" && ! -z "$(tail -c 1 "$file")" ]] && newline=$'\n' || newline=""; echo "$newline$key=$value" >> "$file"; else sed -i'' -E 's/^'"$key"'=.*/'"$key=$value"'/' $file; fi

To set `allow-external-apps` property to `false`.  

    value="false"; key="allow-external-apps"; file="/data/data/com.termux/files/home/.termux/termux.properties"; mkdir -p "$(dirname "$file")"; chmod 700 "$(dirname "$file")"; if ! grep -E '^'"$key"'=.*' $file &>/dev/null; then [[ -s "$file" && ! -z "$(tail -c 1 "$file")" ]] && newline=$'\n' || newline=""; echo "$newline$key=$value" >> "$file"; else sed -i'' -E 's/^'"$key"'=.*/'"$key=$value"'/' $file; fi

• Manual You can do it manually by running the below commands to open the nano text editor in the terminal. Then add/update a line allow-external-apps=true to set the property to true, and press Ctrl+o and then Enter to save and Ctrl+x to exit.

    file="/data/data/com.termux/files/home/.termux/termux.properties";
    mkdir -p "$(dirname "$file")";
    nano "$file"

Draw Over Apps permission (Optional)

For android >= 10 there are new restrictions that prevent activities from starting from the background. This prevents the background TermuxService from starting a terminal session in the foreground and running the commands until the user manually clicks Termux notification in the status bar dropdown notifications list. This only affects plugin commands that are to be executed in a terminal session and not the background ones. Termux version >= 0.100 requests the Draw Over Apps permission so that users can bypass this restriction so that commands can automatically start running without user intervention. You can grant Termux the Draw Over Apps permission from its App Info activity Android Settings -> Apps -> Termux -> Advanced -> Draw over other apps.

Usage

Tasker

1. Create a new Action in a Task.
2. In the resulting Select Action Category dialog, select Plugin.
3. In the resulting Action Plugin dialog, select Termux:Tasker.
4. Click the edit button to edit the configuration.
5. Run the task once the configuration is complete.

Plugin Configuration

The plugin configuration activity can be started by plugin host apps to configure the plugin to define what commands should be run and in which mode. Currently, there are 3 text fields, the Executable, Arguments and Working directory path fields and a Execute in a terminal session toggle. The text fields support plugin host app local variables (all lowercase) like %executable, %arguments or %workdir, you may use multiple variables in a single field.

• The Executable field defines the executable that needs to be run. It can either be set to a file in ~/.termux/tasker/ directory or to an absolute path if allow-external-apps property is set to true (check Setup Instructions). Absolute paths can be like /data/data/com.termux/files/usr/bin/bash. The $PREFIX/ and ~/ prefixes are also supported, like $PREFIX/bin/bash or ~/some-script.

  Execute permissions will automatically be set for the executable file if it exists inside the ~/.termux/tasker/ directory when the plugin action is run. It is the user's responsibility to set read and execute permissions for the executable file if it exists outside the ~/.termux/tasker/ directory. That can be done by running the command chmod 700 "/path/to/executable" from a terminal session before running the plugin action.

• The Arguments field defines the argument that will be passed to the executable. For Termux:Tasker version >= 0.5, arguments will be processed just like there are if commands are run in a shell like bourne shell. It uses ArgumentTokenizer to parse the arguments string.

  Arguemnts are split on whitespaces unless quoted with single or double quotes. Double quotes and backslashes can be escaped with backslashes in arguments surrounded with double quotes.

  Any argument surrounded with single quotes is considered a literal string. However, if an argument itself contains single quotes, then they will need to be escaped properly. You can escape them by replacing all single quotes ' in an argument value with '\'' before passing the argument surrounded with single quotes. So an argument surrounded with single quotes that would have been passed like 'some arg with single quote ' in it' will be passed as 'some arg with single quote '\'' in it'. This is basically 3 parts 'some arg with single quote ', \' and ' in it' but when processed, it will be considered as one single argument with the value some arg with single quote ' in it that is passed to the executable.

  For Tasker, you can use the Variable Search Replace action on an %argument variable to escape the single quotes. Set the Search field to one single quote ', and enable Replace Matches toggle, and set Replace With field to one single quote, followed by two backslashes, followed by two single quotes '\\''. The double backslash is to escape the backslash character itself.

• The Working directory path field for Termux:Tasker version >= 0.5 defines the working directory that should be used while running the command. The directory must be readable by the termux app. It is the user's responsibility to create the directory if its outside the ~/ directory. That can be done by running the command mkdir -p "/path/to/workdir" from a terminal session before running the plugin action. The $PREFIX/ and ~/ prefixes are also supported, like $PREFIX/some-directory or ~/some-directory.

• Execute in a terminal session toggle defines whether the commands will be run in the background or in a foreground terminal session.

  If the toggle is enabled, a new terminal session will open up automatically in the foreground and commands will be run inside it. Result of commands is not returned to the plugin host app.

  If the toggle is not enabled, then commands are run in the background and result of commands is returned to the plugin host app in %stdout, %stderr and %result variables.

  Check Setup Instructions for android >= 10 restrictions that will prevent the commands from automatically starting unless notification is clicked.

Check Templates section for templates that can be used for various configurations.

Plugin Variables

Depending on plugin configuration, the following variables may be returned.

• %stdout containing stdout of commands.
• %stderr containing stderr of commands.
• %result containing exit code of commands. The exit code 0 often means success and anything else is usually a failure of some sort.
• %err containing exit code of plugin action. This will be set only if running the action itself failed like missing permissions or invalid configuration. This may be set by the plugin host app or the plugin. This will not be set if plugin action succeeded.
• %errmsg containing the error message of why the plugin action failed if %err is set.  

If the timeout value of the plugin action is set to 0 or None (slider to extreme left in Tasker), then no variables will be returned, regardless of whether commands need to be run in a foreground terminal session or in background. Even %errmsg will not be set to notify of any errors while running the plugin action since plugin host app will not wait for the plugin to return any variables. This is important for cases like if allow-external-apps is not set to true but an absolute path outside ~/.termux/tasker/ directory is set as the Executable, in which case the plugin action will appear to have succeeded but no commands will execute.

If the timeout value of the plugin action is set to >0 and Execute in a terminal session is not enabled to run commands in background, then the result of commands will be returned in %stdout, %stderr and %result variables. The %err and %errmsgvariables may also be set if the action failed. Note that if the timeout has passed by the time commands finish, the result of command variables will not be set in the plugin host app task and the action will exit with a timeout error, the %err variable will be set to 2 and %errmsg to timeout, at least in Tasker.

If the timeout value of the plugin action is set to >0 and Execute in a terminal session is enabled, then %stdout, %stderr and %result variables will not be returned. Only the %err and %errmsgvariables may be set if the action failed.

The (new) default timeout is set to 10s for all configurations. If you are running background commands that will likely take longer to run, then increase the timeout or set it to Never (slider to extreme right in Tasker). The plugin host app may still get killed by android if it keeps running for long time regardless of timeout value, check here for more info. Even if the commands are to be run in a foreground terminal session, do not set timeout to 0 but use 10s instead, since with timeout 0, plugin host app will not wait for any errors to be returned by the plugin in %err and %errmsg variables and continue the task and the user wouldn't know if any error occurred. Users who already have preexisting actions with the timeout set to 0, like for foreground terminal session commands (considering previous default was 0) should update their tasks and use the new default 10s instead, just opening the configuration screen and returning should automatically do it.  

For Termux:Tasker version >= 0.5, the %errmsg, %stdout, %stderr and %result variables will also be automatically cleared whenever the action is run if timeout is greater than 0 to solve the issue of if multiple actions are run in the same task, then variables from previous action may still be set and get mixed in with current ones. For older versions, you can use a Variable Clear action in Tasker with Pattern Matching enabled and the Name field set to %errmsg/%stdout/%stderr/%result to clear all of them before each plugin action if multiple actions are run in a task or Local Variable Passthrough is enabled in Tasker.

The %err and %errmsg variables will mainly only be set for Termux:Tasker version >= 0.5. These will be set if there are errors like if an executable file is not found, or if allow-external-apps property is not set to true but an absolute path is specified as the executable. Tasker itself may set it too like if Tasker has not been granted the com.termux.permission.RUN_COMMAND permission when running the plugin action or if a timeout occurs, etc.

The %err and %errmsg variables must be stored in another variable with the Variable Set action right after the plugin action if they have to be checked and used later. The plugin host app like Tasker sets and clears %err for each action and it is only available in the next action. To check if and what they are set to, add a Variable Clear action for %command_failed variable before the plugin action, then add a Variable Set action after the plugin action for the %command_failed variable with the value %err %errmsg and If conditions If %err Set OR If %errmsg Set. Then you can just check If %command_failed Set afterward and flash it to notify the user or exit the task if necessary. Error checking should ideally also be done based on %result and optionally the %stderr variables before continuing the task.

Check Templates section for templates on how error and result variables should be handled for various configurations.

Templates

Tasker

• Tasks

  • XML Download the Termux Tasker Plugin Basic Templates Task XML file to the android download directory. To download, right-click or hold the Raw button at the top after opening a file link and select Download/Save link or use curl from a termux shell. Then import the downloaded task file into Tasker by long pressing the Task tab button in Tasker home and selecting Import Task.

    curl -L 'https://github.com/termux/termux-tasker/raw/master/templates/plugin_hosts/tasker/Termux_Tasker_Plugin_Basic_Templates.tsk.xml' -o "/storage/emulated/0/Download/Termux_Tasker_Plugin_Basic_Templates.tsk.xml"

  • Taskernet Import Termux Tasker Plugin Basic Templates Task from Taskernet from here.

  Check Termux Tasker Plugin Basic Templates Task Info file for more info on the task.

• Scripts To use the above task, you will also need to place the termux_tasker_basic_bash_test and termux_tasker_basic_python_test scripts in ~/.termux/tasker/ directory after following its Setup Instructions. They basically just print the first 2 args to stdout if only 2 args are received, otherwise exit with error.

  1. Download the script files.

     • Download to ~/.termux/tasker/ directly from github using curl using a non-root termux shell.

       curl -L 'https://github.com/termux/termux-tasker/raw/master/templates/scripts/termux_tasker_basic_bash_test' -o "/data/data/com.termux/files/home/.termux/tasker/termux_tasker_basic_bash_test"

       curl -L 'https://github.com/termux/termux-tasker/raw/master/templates/scripts/termux_tasker_basic_python_test' -o "/data/data/com.termux/files/home/.termux/tasker/termux_tasker_basic_python_test"

     • Download them manually to android download directory and then use cat to copy them to ~/.termux/tasker/ or manually do it with a SAF file browser.

       cat "/storage/emulated/0/Download/termux_tasker_basic_bash_test" > "/data/data/com.termux/files/home/.termux/tasker/termux_tasker_basic_bash_test"

       cat "/storage/emulated/0/Download/termux_tasker_basic_python_test" > "/data/data/com.termux/files/home/.termux/tasker/termux_tasker_basic_python_test"

  2. Set executable permissions.

     chmod 700 "/data/data/com.termux/files/home/.termux/tasker/termux_tasker_basic_bash_test"

     chmod 700 "/data/data/com.termux/files/home/.termux/tasker/termux_tasker_basic_python_test"

  To modify the scripts you can use nano.

  nano "/data/data/com.termux/files/home/.termux/tasker/termux_tasker_basic_bash_test"
nano "/data/data/com.termux/files/home/.termux/tasker/termux_tasker_basic_python_test"

Termux needs to be granted Storage permission to allow it to access /storage/emulated/0/Download directory, otherwise you will get permission denied errors while running commands.

Creating And Modifying Scripts

You can create scripts in ~/.termux/tasker/ directory after following its Setup Instructions. Scripts can also be created elsewhere in Termux files directory but will require allow-external-apps to be set to true for the plugin to access them.

You can use shell based text editors like nano, vim or emacs to create and modify scripts.

nano "/data/data/com.termux/files/home/.termux/tasker/some_script"

You can also use GUI based text editor android apps that support SAF. Termux provides a Storage Access Framework (SAF) file provider to allow other apps to access its ~/ home directory. However, the $PREFIX/ directory is not accessible to other apps. The QuickEdit or QuickEdit Pro app does support SAF and can handle large files without crashing, however, it is closed source and its pro version without ads is paid. You can also use Acode editor or Turbo Editor if you want an open source app.

Note that the android default SAF Document file picker may not support hidden file or directories like ~/.termux which start with a dot ., so if you try to use it to open files for a text editor app, then that directory will not show. You can instead create a symlink for ~/.termux at ~/termux_sym so that it is shown. Use ln -s "/data/data/com.termux/files/home/.termux" "/data/data/com.termux/files/home/termux_sym" to create it.

Debugging

You can help debug problems like how arguments are being parsed by the plugin or if the plugin is even firing etc by setting appropriate logcat Log Level in options menu (3 dots) in the plugin configuration screen. Note that whatever log level is set will affect the entire plugin app and all plugin actions and not just for the action whose configuration you used to set it. The setting only exists inside the configuration activity of actions because creating a separate launcher activity that would be shown in the list of apps in the launcher just for this setting doesn't seem worth it. Log Level defaults toNormal and log level Debug currently logs additional information. Its best to revert log level to Normal after you have finished debugging since private data may otherwise be passed to logcat during normal operation and moreover, additional logging increases execution time.

For information on how to view the logcat logs, check official android guide here.

Log Levels

• Off - Log nothing
• Normal - Start logging error, warn and info messages and stacktraces
• Debug - Start logging debug messages
• Verbose - Start logging verbose messages

Worthy Of Note

Arguments and Result Data Limits

There are limits on the arguments size you can pass to commands or the full command string length that can be run, which is likely equal to 131072 bytes or 128KB for an android device defined by ARG_MAX but after subtracting shell environment size, etc, it will roughly be around 120-125KB but limits may vary for different android versions and kernels. You can check the limits for a given termux session by running true | xargs --show-limits. If you exceed the limit, you will get exceptions like Argument list too long. You can manually cross the limit by running something like $PREFIX/bin/echo "$(head -c 131072 < /dev/zero | tr '\0' 'a')" | tr -d 'a', use full path of echo, otherwise the echo shell built-in will be called to which the limit does not apply since exec is not done.

Moreover, exchanging data between Tasker and Termux:Tasker is done using Intents, like sending the command and receiving result of commands in %stdout and %stderr. However, android has limits on the size of actual data that can be sent through intents, it is roughly 500KB on android 7 but may be different for different android versions.

Basically, make sure any data/arguments you send to Termux:Tasker is less than 120KB (or whatever you found) and any expected result sent back is less than 500KB, but best keep it as low as possible for greater portability. If you want to exchange an even larger data between tasker and termux, use physical files instead.

The argument data limits also apply for the RUN_COMMAND Intent intent.

Termux Environment

Termux does not load the environment fully for external plugins or RUN_COMMAND Intent commands, like setting LD_PRELOAD, so any external scripts which do not have shebangs to full path to termux bin directory will not work if called from inside your plugin scripts, since libtermux-exec.so is not called since LD_PRELOAD isn't set and you will get bad interpreter: No such file or directory errors. Simply setting LD_PRELOAD will not work either without starting a new shell. So make sure to set the shebangs correctly for any external scripts you want to run from inside your plugin script. The correct shebangs for termux scripts are like #!/data/data/com.termux/files/usr/bin/bash for bash scripts instead of #!/usr/bin/bash used in common linux distros. You can also use termux-fix-shebang command on the external scripts before running them with the plugin to fix the shebangs automatically.

Defining Scripts In Plugin Host App

Currently, any script files that need to be run need to be created in ~/.termux/tasker/ directory. It may get inconvenient to create physical script files for each type of command you want to run. These script files are also neither part of backups of plugin host apps like Tasker and require separate backup methods and nor are part of project configs shared with other people or even between your own devices, and so the scripts need to be added manually to the ~/.termux/tasker/ directory on each device. To solve such issues and to dynamically define scripts of different interpreted languages inside your plugin host app like Tasker and to pass them to Termux as arguments instead of creating script files, tudo can be used for running commands in termux user context and sudo for running commands with super user (root) context, check their script command type. These scripts will also load the termux environment properly like setting LD_PRELOAD etc before running the commands.

License

Released under the GPLv3 license.