How to set commands output as a variable in a batch file

Question

Is it possible to set a statement\'s output of a batch file to a variable, for example:

findstr testing > %VARIABLE%

echo %VARIABLE%

Answer 1

These answers were all so close to the answer that I needed. This is an attempt to expand on them.

In a Batch file

If you're running from within a .bat file and you want a single line that allows you to export a complicated command like jq -r ".Credentials.AccessKeyId" c:\temp\mfa-getCreds.json to a variable named AWS_ACCESS_KEY then you want this:

FOR /F "tokens=* USEBACKQ" %%g IN (`jq -r ".Credentials.AccessKeyId" c:\temp\mfa-getCreds.json`) do (SET "AWS_ACCESS_KEY=%%g")

On the Command Line

If you're at the C:\ prompt you want a single line that allows you to run a complicated command like jq -r ".Credentials.AccessKeyId" c:\temp\mfa-getCreds.json to a variable named AWS_ACCESS_KEY then you want this:

FOR /F "tokens=* USEBACKQ" %g IN (`jq -r ".Credentials.AccessKeyId" c:\temp\mfa-getCreds.json`) do (SET "AWS_ACCESS_KEY=%g")

Explanation

The only difference between the two answers above is that on the command line, you use a single % in your variable. In a batch file, you have to double up on the percentage signs (%%).

Since the command includes colons, quotes, and parentheses, you need to include the USEBACKQ line in the options so that you can use backquotes to specify the command to run and then all kinds of funny characters inside of it.