Running multiple commands with su in Bash

This command runs fine:

su root -c "date; ls -lh"

But in this command:

su root -c "tcpdump -i wlan0 -s 1500 -w CCCCCC & ; ls -lh;"

Since you have & before ; therefore you are getting errors. Try removing & and re-executing the command.

Or you can run your command like this:

su root -c "(tcpdump -i wlan0 -s 1500 -w CCCCCC &); ls -lh"

As anubhava says, your

su root -c "tcpdump -i wlan0 -s 1500 -w CCCCCC & ; ls -lh;"

command is failing because you’re not allowed to have & followed immediately by ;.  You can see this just by typing the commands directly into the shell:

• true & true  works
• true & ; true doesn’t work

If you want the tcpdump command to run in the background, remove the ;, as in

su root -c "tcpdump -i wlan0 -s 1500 -w CCCCCC & ls -lh;"

(and you don't need the ; at the end, either, but it doesn’t hurt).