How to store standard error in a variable

Question

Let\'s say I have a script like the following:

useless.sh

echo \"This Is Error\" 1>&2
echo \"This Is Output\" 

And I have an

Answer 1

There are a lot of duplicates for this question, many of which have a slightly simpler usage scenario where you don't want to capture stderr and stdout and the exit code all at the same time.

if result=$(useless.sh 2>&1); then
    stdout=$result
else
    rc=$?
    stderr=$result
fi

works for the common scenario where you expect either proper output in the case of success, or a diagnostic message on stderr in the case of failure.

Note that the shell's control statements already examine $? under the hood; so anything which looks like

cmd
if [ $? -eq 0 ], then ...

is just a clumsy, unidiomatic way of saying

if cmd; then ...