Actually there are - but not using exec. Let me first explain the use of exec, then what you can do to fulfill your requirement.

The keyword exec is used for two very different purposes: the first is to replace (instead of fork) the current process. Consider this script part:

Code:

command1
command2

What happens when the shell executes this is:

1) create a subprocess and start command1 in this
2) wait until this subprocess has finished
3) create another subprocess and start command2 in it
etc..

As long as it takes i.e. command1 to run you would see the process of your script (say, yourscript.sh) in the process list as parent process and command1 as child process. exec instead will replace the running script (effectively stopping its execution) with the command in question, which will take over the process number and everything else of the - up to now - running script. That means:

Code:

exec command1
command2

would be pointless because after the first line being executed the script is not running any more and hence command2 will never be executed. So, in this sense, two exec in one script would not make sense - except, of course, if there is some condition attached to it:

Code:

if <condition> ; then
     exec command1
else
     exec command2
fi

The second purpose - without any command but a redirection instead - of exec is to redirect I/O as you have done. The problem regarding your goal is not so much exec itself but a property of UNIX processes: processes have (per default) one input - <stdin> - and two outputs: <stdout> and <stderr>. Any of these "I/O descriptors", as the correct wording is, can point to any source providing a data stream: a file, a device, a pipeline, ... exec > /some/where is just a fancy way of directing the <stdout> I/O descriptor to that certain file.

You can use several such execs to re-redirect these streams to various sources/targets, but each such redirection will overwrite the previous one. Not because of the way exec works, but because each I/O-descriptor can either point this way or that way, but not both. Picture a UNIX process as a sort-of garden hose: you fill something in at one end and something comes out on the other. You can use what comes out to fill this bucket or that bucket, but not both at the same time.

For such a thing - to fill both buckets at the same time - you would need a "T-piece", as plumbers call it: something to divide the water stream into two water streams. Exactly this analogy inspired the makers of UNIX to create the tee utility. You can use it to duplicate an output stream so that it will go to two different targets at the same time. You cannot use that inside the script but you can use it outside with a redirection:

Code:

yourscript.sh | tee /some/file >/other/file

will write <stdout> of yourscript.sh to both /some/file and /other/file. I suggest you read the man page of tee to get acquainted. If you still need help just ask.

I hope this helps.

bakunin