There are already some existing questions asked here about running commands as another user. However, the question and answers focus on a single command instead of a long group of commands.
For example, consider the following script:
#!/bin/bash
set -e
root_command -p param1 # run as root
# these commands must be run as another user
command1 -p 'parameter with "quotes" inline'
command2 -p 'parameter with "quotes" inline'
command3 -p 'parameter with "quotes" inline'
There are a couple of important points to note here:
The final three commands must be run as another user using su or sudo. In the example there were three commands, but suppose that there were many more...
The commands themselves make use of single and double quotes.
The second point above prevents the use of the following syntax:
su somebody -c "command"
...since the commands themselves contain quotes.
What is the proper way to "group" the commands and run them under another user account?
Try this:
su somebody <<'EOF'
command1 -p 'parameter with "quotes" inline'
command2 -p 'parameter with "quotes" inline'
command3 -p 'parameter with "quotes" inline'
EOF
<< introduces a here-doc. The next token is the delimiter, and everything up to a line beginning with the delimiter is fed as standard input to the command. Putting the delimiter in single quotes prevents variable substitution within the here-doc.