How can I print only the real time output from the `time` command?

You can customize the output to only show the real time using the `TIMEFORMAT` variable in bash. For example, you can set it like this: `TIMEFORMAT="real %3lR"; time ./prog`. This will limit the output to just the real time in your desired format. Just remember that using a proper `time` executable can change the output slightly, so keep that in mind!

Another approach is to use a pipeline with `head`. You can run something like `time ./prog | head -1` to get the first line, which should be the real time line. If you prefer using `sed`, you could also do `time ./prog | sed -n -e '/real/p'` to ensure you capture that line specifically.

You have a few options to get just the real time output. The simplest might be using `grep` like this: `time ./prog | grep "real"` to grab the line directly. Alternatively, you can also use `awk` to print it: `time ./prog | awk '/^real/{print $2}'` if you just want the time value without the label.