1648407_how-to-reverse-command-ubuntu

ShellCheck.net gives this:

$ shellcheck myscript

Line 1:
sudo sed -i "s/#user = "root"/user = "$(id -un)"/g" /etc/libvirt/qemu.conf
^-- SC2148: Tips depend on target shell and yours is unknown. Add a shebang or a 'shell' directive.
                        ^-- SC2140: Word is of the form "A"B"C" (B indicated). Did you mean "ABC" or "A\"B\"C"?
                                      ^-- SC2027: The surrounding quotes actually unquote this. Remove or escape them.
                                      ^-- SC2046: Quote this to prevent word splitting.

$

Line 1	SC2148: Tips depend on target shell and yours is unknown. Add a shebang or a 'shell' directive.
Line 1	SC2140: Word is of the form "A"B"C" (B indicated). Did you mean "ABC" or "A\"B\"C"?
Line 1	SC2027: The surrounding quotes actually unquote this. Remove or escape them.
Line 1	SC2046: Quote this to prevent word splitting.