What’s the Best Way to Measure Command Execution Time in Terminal?

You can simply prepend `time` to your command if you're using a bash shell. This will give you the execution time directly. Check the man page for more details: https://www.man7.org/linux/man-pages/man1/time.1.html

In Linux, you can just run `time python3 prog.py`. If you're looking for millisecond precision, you can implement a small Python script:
```python
import time

start = time.perf_counter()
# your code here
end = time.perf_counter()

elapsed_ms = (end - start) * 1000
print(f"Elapsed: {elapsed_ms:.3f} ms")
```
For Powershell, try:
```powershell
(Measure-Command { python your_script.py }).TotalMilliseconds
```
And in CMD, you can use:
```cmd
set start=%TIME%
python your_script.py
set end=%TIME%
echo Start: %start%
echo End: %end%
```

If you want a shell function that gives you time in milliseconds, here's one I use:
```sh
TIME_EXEC_MS() {
local t_start
local t_end
t_start=$(date +%s%N)
"$@" > /dev/null
local ret=$?
t_end=$(date +%s%N)
t_elapsed=$(( (t_end - t_start) / 1000000 )) # ms
echo "${t_elapsed}"
return $ret
}
```

You can call it like this: `TIME_EXEC_MS python3 myprog.py` and if you want to run it multiple times, I have another function to repeat commands.

There are two options for timing: the bash builtin `time` or the `/usr/bin/time` command. For Python, you might also want to use the `timeit` module, which is really handy for precise timing.