Bash grouping commands

Something I was struggling when creating the static site generator in bash was:

1. How I can temporary change directory execute some tasks and back to the previous working directory.
2. How I had no idea how to append different output together to form a file content

Regarding the directory change I remember using pushd and popd, but I had no luck and no way to figure it out why it wasn't working as I expected.

For some luck change, I didn't know what to look for, but found this page about Grouping Commands, which are exactly what I was looking for, and solve both of my problems.

There are two ways to group commands; one it's using parenthesis or curly braces. Using the parenthesis creates a subshell, allowing us to change directory inside it, but on outside the shell the working directory is maintained.

pwd
(
    cd /path/to/directory
    pwd
)
pwd

# Output
/home/user
/path/to/directory
/home/user

Using curly braces helps me put everything between them and whatever was the output I can redirect them to the file.

I went from something like the code below:

echo "<styles>" >> "$tmp"
echo "$styles" >> "tmp"
echo "</style>" >> "$tmp"

To something like this:

{
    echo "<styles>"
    echo "$styles"
    echo "</styles>"
} > "$tmp"