hi guys, how would you do the following? I have a menu with 5 options in my shell script:

1. Run function 1 against files
2. Run function 2 against files
3. Run function 3 against files
4. Run function 4 against files
5. Run function 5 against files

I'd like to be able to run multiple functions however based on what the user inputs, for for example if I press key 1,2 and 4 then I want to run function 1, 2 and 4, if I press key 1 and 4 then only run function 1 and 4, if i just press key number 1 then i only want to run function 1 - any ideas?

Depends on how you wrote your menu script:
How do you capture the input? in sequence on in one go?

What are these functions? should they be running at the same time or one after the other...

They can just run one after the other, it's just a read:

read rSelection
if [[ $rSelection == '1' ]] then
    #call function 1
    else
    if [[ $rSelection == '2' ]] then
    #call function 2
    else
    if [[ $rSelection == '3' ]] then
    #call function 3
    else
    if [[ $rSelection == '4' ]] then
    #call function 4
    else
    if [[ $rSelection == '5' ]] then
    #call function 5
    else
    echo "Exiting"
    exit
    fi
fi

Try something like:

f1 () { 
echo running fn1 
}
 
f2 () {
echo running fn2 
}
 
f3 () { 
echo running fn3 
}
 
f4 () { 
echo running fn4 
}
 
echo "enter choice -- multiple choice can be provided separated by space"
 
read choice
 
set -- $choice
 
for i in $@
do
 echo "run function $i"
 f${i}
done

What I see (but its friday...) is ONE read
so all your values (or just one) are read in one go.
One way to do things would be to stripe the entry ( what do you see when you enter 123? do you get 1 2 3 or 123? in other words is there a separator?) and use the values in a loop
That would give you something like:

for i in $rSelection  (if there were a blank between the values) # but you could use while...
do
   <Your if paragraph
    fi >
done

That's a good point.

for i in $choice
do
 echo "run function $i"
 f${i}
done

cheers guys, not really following though

for i in $choice
do
 echo "run function $i"
 f${i}
done