I have something like this
command \
second line of command \
...
...
How do I confirm so it executes?
The backslash (\) at the end of the line continues the command to the next line. Don't end the last line of the command with a backslash and it will execute the whole command.
If you have an unclosed quote (" or '), the command also won't complete until you close the quote. Also some uncompleted commands are detected and continue to prompt you for the rest of the command. In bash, simply typing 'if' for example won't complete until the shell sees the terminating 'fi'.
The first line not ending with a '\' will execute it.