The issue in your Bash script is due to how pipes (|) and variable scoping work in Bash.

Explanation:

• echo hey | read test: This line pipes the output of echo hey to the read test command. However, in Bash, each command in a pipeline runs in its own subshell. This means the read test command executes in a subshell, and the variable test is only set within that subshell.
• echo $test: This line runs in the parent shell, where the variable test was never set (because it was set in a subshell). Thus, $test is empty, and nothing is printed.

Why This Happens:

• Subshells in Pipelines: In Bash, pipelines create subshells for each command. Variables set in a subshell do not persist in the parent shell.
• No Variable Propagation: The variable test is local to the subshell created by the pipeline and is not available in the parent shell where echo $test runs.

How to Fix It:

If you want to capture the output of echo hey into the variable test and use it later, avoid using a pipe with read. Instead, use command substitution:

bash
Copy
test=$(echo hey)
echo $test

This will correctly set test to hey and print it.

Alternatively, if you want to use read, you can do it like this:

bash
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echo hey | { read test; echo $test; }

But this still only works within the same subshell. To use test later, you need to avoid the subshell, as in the first example.