If you're only installing that one small script, I'd just do it manually. You could use a
shar file, but that seems like overkill.
The biggest issues I see are first, that
bash is going to be located in different locations on different systems, but there's nothing in your script that's Bash-specific, so you could change your shebang to:
Second, you will need to choose a location for your script. It strikes me that
/usr/local/bin would be as good as any.
Third, you will need to
chown to set the ownership and
chmod to set the permissions.
Fourth, you should choose better locations for your output files. If they are only for temporary use, then they should be created in
/tmp rather than the root directory where you have
suid.new going, or the current directory where you have
newchanges going. Otherwise, somewhere in
var might be where you'd want to put more persistent data. Perhaps
exit prevents the second
if from ever being evaluated so no mail will ever be sent.
Sixth, you might want to
mv suid.new suid.old at some point so the next time you do your check it's comparing the most recent saved data.
Seventh, your last mail command should have the file piped or redirected in. It won't work as an argument. And the two mail commands should be swapped so you're not mailing a file when it's empty and are mailing it when it's not.
if [ -s "/newchanges" ]
mail -s "No changes have occurred" firstname.lastname@example.org < /path/to/newchanges
mail -s "changes have occurred" email@example.com