The error occurs because you are writing the function definition to the file test.sh as a string, not as executable Bash code. When you run:

echo my_test > test.sh

You are literally writing the text my_test into test.sh, not the function definition. So, when you run bash test.sh, it tries to execute my_test as a command, which doesn't exist.

How to Fix It

To write the function to test.sh and make it executable, you need to write the entire function definition to the file. Here's how:

Correct Approach

cat << 'EOF' > test.sh
my_test() {
    echo test
}
my_test
EOF
bash test.sh

Explanation:

• cat << 'EOF' > test.sh writes everything between EOF to test.sh.
• The function my_test is properly defined in the file.
• my_test is called at the end of the file, so it executes when you run bash test.sh.

Output:

test

Alternative (Directly Writing the Function)

If you want to write the function directly from the command line:

echo 'my_test() { echo test; }' > test.sh
echo 'my_test' >> test.sh
bash test.sh

This will also work and produce the same output.