A Termux plugin app allowing Termux commands to be executed from Tasker and other plugin host apps.
- Installation
- Setup Instructions
- Usage
- Plugin Configuration
- Plugin Variables
- Templates
- Creating And Modifying Scripts
- Debugging
- Worthy Of Note
- For Maintainers and Contributors
- Forking
Latest version is v0.6.0.
Check termux-app Installation for details before reading forward.
Termux:Tasker application can be obtained from F-Droid from here.
You do not need to download the F-Droid app (via the Download F-Droid link) to install Termux:Tasker. You can download the Termux:Tasker APK directly from the site by clicking the Download APK link at the bottom of each version section.
It usually takes a few days (or even a week or more) for updates to be available on F-Droid once an update has been released on Github. The F-Droid releases are built and published by F-Droid once they detect a new Github release. The Termux maintainers do not have any control over the building and publishing of the Termux apps on F-Droid. Moreover, the Termux maintainers also do not have access to the APK signing keys of F-Droid releases, so we cannot release an APK ourselves on Github that would be compatible with F-Droid releases.
The F-Droid app often may not notify you of updates and you will manually have to do a pull down swipe action in the Updates tab of the app for it to check updates. Make sure battery optimizations are disabled for the app, check https://dontkillmyapp.com/ for details on how to do that.
Termux:Tasker application can be obtained on Github either from Github Releases for version >= 0.6.0 or from Github Build action workflows.
The APKs for Github Releases will be listed under Assets drop-down of a release. These are automatically attached when a new version is released.
The APKs for Github Build action workflows will be listed under Artifacts section of a workflow run. These are created for each commit/push done to the repository and can be used by users who don't want to wait for releases and want to try out the latest features immediately or want to test their pull requests. Note that for action workflows, you need to be logged into a Github account for the Artifacts links to be enabled/clickable. If you are using the Github app, then make sure to open workflow link in a browser like Chrome or Firefox that has your Github account logged in since the in-app browser may not be logged in.
The APKs for both of these are debuggable and are compatible with each other but they are not compatible with other sources.
Termux and its plugins are no longer updated on Google Play Store due to android 10 issues and have been deprecated. It is highly recommended to not install Termux apps from Play Store any more. Check https://github.com/termux/termux-app#google-play-store-deprecated for details.
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 bootstrap 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 and can also be referred by the $PREFIX shell environment variable. The ~/ is a shortcut for the Termux home directory and can also be referred by the $HOME shell environment variable. Note that ~/ will not expand inside single or double quotes when running commands. Permissions and ownerships can be checked with the stat <path> command.
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.
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.
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
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.
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Automatic You can use the one-liner commands below to set the desired value. The commands will append the desired value using
echocommand to the file if the file doesn't exist or the property doesn't exist in the file, otherwise it willsedreplace any existing values of the key with the desired value.To set
allow-external-appsproperty totrue.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"'/' $file; fiTo set
allow-external-appsproperty tofalse.value="false"; key="allow-external-apps"; file="/data/data/com.termux/files/home/.termux/termux.properties"; mkdir -p "$(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"'/' $file; fi -
Manual You can do it manually by running the below commands to open the
nanotext editor in the terminal. Then add/update a lineallow-external-apps=trueto set the property totrue, and pressCtrl+oand thenEnterto save andCtrl+xto exit.
file="/data/data/com.termux/files/home/.termux/termux.properties";
mkdir -p "$(dirname "$file")";
nano "$file"
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.
- Create a new
Actionin aTask. - In the resulting
Select Action Categorydialog, selectPlugin. - In the resulting
Action Plugindialog, selectTermux:Tasker. - Click the edit button to edit the configuration.
- Run the task once the configuration is complete.
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.
The text fields support plugin host app local variables (all lowercase) like %executable, %arguments, %workdir, %stdin, etc and you may use multiple variables in a single field.
The Executable text 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 text 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 text 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 for version < 0.6.0 and /data/data/com.termux/files directory for version >= 0.6.0. 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.
The Stdin text field for Termux:Tasker version >= 0.6.0 can be used to pass scripts via standard input (stdin), like a bash script to the $PREFIX/bin/bash shell and a python script to the $PREFIX/bin/python shell or any other commands. This allows scripts to be defined in the plugin host app instead of defining physical script files in ~/.termux/tasker/ directory. Check Defining Scripts In Plugin Host App for details.
Note that if passing script via stdin, do not pass arguments, since it will fail depending on shell, at least will for bash.
The max supported length of a script is 45K characters taking into consideration the Tasker plugin bundle limits of 100KB when its stored in a Parcel. On Android 7-11, the String characters are stored in Parcel as UTF-16, i.e 2 bytes. So we use 10KB for rest of the plugin configuration data and half of the remaining (90KB) for storing the script.
The Terminal Session Action text field for Termux:Tasker version >= 0.6.0 defines what should happen when a foreground session command is received for the Termux. The user can define whether the new session should be automatically switched to or if existing session should remain as the current session. The user can also define if foreground session commands should open the TermuxActivity or if they should run in the "background" in the Termux notification. The user can click the notification to open the sessions. The valid values are defined by TermuxConstants.TERMUX_APP.TERMUX_SERVICE.VALUE_EXTRA_SESSION_ACTION_*, currently, between 0 and 3.
The Custom Log Level text field for Termux:Tasker version >= 0.6.0 defines the log level for background commands that should be used by Termux.
By default Termux only logs command stdout and stderr to logcat if user has set log level to VERBOSE in Termux app settings (not Termux:Tasker). However, if command outputted too much data to logcat, then logcat clients like in Android Studio would crash.
So one can pass a custom log level that is >= to the log level set it Termux app settings where (OFF=0, NORMAL=1, DEBUG=2, VERBOSE=3) for custom behaviour. If you pass 0, it will completely disable logging. If you pass 1, logging will only be enabled if log level in termux settings is NORMAL or higher. If custom log level is not passed, then default behaviour will remain and log level in Termux app settings must be VERBOSE or higher for logging to be enabled. Note that the log entries will still be logged with priority Log.VERBOSE regardless of log level, i.e logcat will have V/.
The entries logcat component will be TermuxCommand. For output at stdout, the entry format is [<pid>-stdout] ... and for the output at stderr, the entry format is [<pid>-stderr] .... The <pid> will be the process id (pid) as an integer that was started by Termux for the executable. For example: V/TermuxCommand: [66666-stdout] ....
Instead of using am command to send messages back to Tasker, you can use Tasker Logcat Entry profile event to listen to messages from Termux at both stdout and stderr. This might be faster than am command intent systems or at least possibly more convenient in some use cases.
So setup a profile with the Component value set to TermuxCommand and Filter value set to -E 'TermuxCommand: \[[0-9]+-((stdout)|(stderr))\] message_tag: .*' and enable the Grep Filter toggle so that entry matching is done in native code. Check Tasker Logcat Info documentation for details. Also enable Enforce Task Order in profile settings and set collision handling to Run Both Together so that if two or more entries are sent quickly, entry task is run for all. Tasker currently (v5.13.16) is not maintaining order of entry tasks despite the setting.
Then start a Termux:Tasker plugin action with custom log level 1 (assuming current log level is NORMAL) and you should be able to receive the entries for whatever you send to stdout and stderr in your script that starts with message_tag: as %lc_text in entry task of tasker Logcat Entry profile. You can remove the prefix from the %lc_text variable with Variable Search Replace action. Set the Search field to TermuxCommand: \[[0-9]+-((stdout)|(stderr))\] message_tag: , and enable Replace Matches toggle, and leave Replace With empty.
The 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 for version < 0.6.0. For version >= 0.6.0, result will be returned in %stdout and %result variables. The %stdout variable will only contain the session transcript and will contain both stdout and stderr combined, basically anything sent to the the pseudo terminal /dev/pts, including PS1 prefixes for interactive sessions. For foreground commands that exited with failure will require Termux app version >= 0.118.0 for sessions to automatically close without waiting for user to press enter.
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.
The Wait for result for commands toggle for Termux:Tasker version >= 0.6.0 defines whether the plugin action should wait for result of commands. It will apply to both foreground session and background commands. Check Plugin Variables for details.
Check Templates section for templates that can be used for various configurations.
Depending on plugin configuration, the following variables may be returned.
%stdoutcontainingstdoutof commands.%stdout_original_lengthcontaining original length ofstdout.%stderrcontainingstderrof commands.%stderr_original_lengthcontaining original length ofstderr.%resultcontainingexit codeof commands. Theexit code0often means success and anything else is usually a failure of some sort.%errcontainingexit codeof 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.%errmsgcontaining the error message of why the plugin action failed if%erris 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 Wait for result for commands toggle is enabled, then the result of commands will be returned in %stdout, %stderr (only background) and %result variables. The %err and %errmsg variables 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 Wait for result for commands toggle is not 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.
The %stdout_original_length and %stderr_original_length can be used to check if %stdout and %stderr were truncated by Termux app before sending them back to plugin host app in case they were too large and would have triggered TransactionTooLargeException. The stdout and stderr sent back will be truncated from the start to max 100KB combined. The errmsg will also be truncated from end to max 25KB. Check here and here for details.
Check Templates section for templates on how error and result variables should be handled for various configurations.
The templates were written for version < 0.6.0 and currently have not been updated for version >= 0.6.0.
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Tasks-
XMLDownload the Termux Tasker Plugin Basic Templates Task XML file to the android download directory. To download, right-click or hold theRawbutton at the top after opening a file link and selectDownload/Save linkor usecurlfrom a termux shell. Then import the downloaded task file into Tasker by long pressing theTasktab button in Tasker home and selectingImport 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" -
TaskernetImportTermux Tasker Plugin Basic Templates TaskfromTaskernetfrom here.
Check Termux Tasker Plugin Basic Templates Task Info file for more info on the task.
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ScriptsTo 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 first2args tostdoutif only2args are received, otherwise exit with error.-
Download the script files.
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Download to
~/.termux/tasker/directly from github usingcurlusing 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
catto 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"
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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.
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 ~/.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.
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 or in Termux app settings -> Termux:Tasker -> Debugging -> Log Level (Requires Termux app version >= 0.113). 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. The Log Level defaults to Normal and log level Verbose 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.
The plugin does not execute the commands itself but sends an execution intent to Termux app, which has its own log level which can be set in Termux app settings -> Termux -> Debugging -> Log Level. So you must set log level for both Termux and Termux:Tasker app settings to get all the info.
Once log levels have been set, you can run the logcat command in Termux app terminal to view the logs in realtime (Ctrl+c to stop) or use logcat -d > logcat.txt to take a dump of the log. You can also view the logs from a PC over ADB. For more information, check official android logcat guide here.
Off- Log nothing.Normal- Start logging error, warn and info messages and stacktraces.Debug- Start logging debug messages.Verbose- Start logging verbose messages.
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. The Termux app based on testing still sets a safe limit at 100KB and will truncate any data higher than that. Check %stdout_original_length and %stderr_original_length in Plugin Variables section for details.
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 100KB, 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.
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 or use tudo/sudo mentioned below.
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, you can either use Stdin plugin configuration field or use tudo or sudo.
The tudo script can be used for running commands in termux user context and the sudo script 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. There are much more customizable then using Stdin and support things that aren't possible to be provided via the plugin.
Check For Maintainers and Contributors section of termux/termux-app README for details.
Check Forking section of termux/termux-app README for details.