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I want to type a script into something like a heredoc and execute it without writing to a file first.

I use a Teensy3.2 microcontroller with an attached sdcard to automatically type out some repetitive tasks (like a USB macro keyboard).

Why? I have computers on which permanent file system changes/mass storage devices are not permitted and I have repetitive tasks that benefit from shell scripting.

But, I find this so very useful that I would like to load unmodified shell scripts onto the SDcard and execute them. The teensy can only type them out (no mass storage). Typing them out into a file requires them to be saved to the filesystem and execute permission granted before they can be executed and ultimately deleted.

I'm not real happy with this. It seems a bit hacky and I don't like automating file deletions with a "keyboard macro".

I've tried ssh << EOF etc... // but different computers require different passwords that aren't stored in the (unmodified) scripts and ssh does prompt for passwords and I am not permitted to change this configuration.

I've also tried exec << EOF etc... but I don't understand the behavior since it kills my shell when finished (which scares me).

Basically I want to:

Keyboard.print("exec << 'EOF'");
while (sdcardScriptFile.available()) {
  Keyboard.write(sdcardScriptFile.read());
}
Keyboard.print("EOF");

Would it be better to just open a subshell and type out each line of the script? If so, would I just:

Keyboard.print("(");
while (sdcardScriptFile.available()) {
  Keyboard.write(sdcardScriptFile.read());
}
Keyboard.print(")");

I would like to be able to add scripts to the SDcard and have them available to be typed and executed "on the fly" without making changes to the filesystem.

Jason Rogachesky
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  • `sh -s < – Biffen Jun 28 '19 at 06:40
  • One thing I do is have my script in a file on my PC. I open it in an editor, select all, copy and paste it in the terminal window. I have never seen a bash script fail because of that. But I am not sure if that is what you want. – Nic3500 Jun 28 '19 at 16:27

1 Answers1

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If it needs to be run in the current shell process, you could source it.

Keyboard.print(". /dev/fd/0 << 'EOF'");
while (sdcardScriptFile.available()) {
  Keyboard.write(sdcardScriptFile.read());
}
Keyboard.print("EOF");
Dabombber
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