The issue is due to how the script test.sh is structured and how input/output is handled in Bash. Let's break it down:

Problem Analysis

1. adb shell exit:

   • This command attempts to exit an adb shell session. If there is no active adb shell session, this command will fail silently (or with an error, depending on your environment).
   • However, it does not terminate the script itself. The script continues to the next line.

2. read test:

   • The read command waits for user input from stdin (standard input).
   • In your case, you are piping echo hey into the script (echo hey | ./test.sh), so the script receives hey as input for the read command.
   • However, the read command consumes the entire input (hey), but the script does not explicitly output anything after reading it.

3. echo $test:

   • This line prints the value of the variable test, which was set by the read command.
   • However, the output of echo $test is not being captured or displayed in your terminal because the script's output is not being explicitly directed to stdout in a way that is visible in this context.

Why No Output?

• The script reads the input (hey) into the variable test, but the echo $test output is not being displayed because:
  • The script is being executed in a subshell (due to the pipe |), and the output of echo $test is not being passed back to the terminal.
  • The script does not explicitly return or print anything to stdout in a way that is visible when run via a pipe.

How to Fix It

If you want the script to output the value of test when run with echo hey | ./test.sh, you need to ensure the script explicitly prints the output to stdout. For example:

#!/bin/bash

adb shell exit

read test
echo "$test"  # Explicitly print the value of $test

Now, running:

echo hey | ./test.sh

will output:

hey

Key Takeaway

• The script was not explicitly printing the output of echo $test in a way that was visible when run via a pipe.
• The read command consumed the input, but the script did not explicitly return or display the output.