It’s often useful to see how long a command took to run. I used to have the date and time in my prompt for that reason–I could do some mental arithmetic to find out how long a command took.

But, I’ve been trying to make my prompt more minimal after being inspired by @topfunky’s zen-like prompt, and the date and time clutter it up.

So, I patched fish to measure how long commands take to run, and write the duration to an environment variable when it’s useful (i.e. more than a second).

The patch is in my fish fork. Here’s the high-level part of it:

    term_donate();

+   gettimeofday(&time_before, NULL);
+
    eval( cmd, 0, TOP );
    job_reap( 1 );

+   gettimeofday(&time_after, NULL);
+   set_env_cmd_duration(&time_after, &time_before);
+
    term_steal();

The call to eval() is where the command is run, so that’s the call that will block and take time. I’m using gettimeofday() to grab a unix timestamp directly before and after the call, and then a new function set_env_cmd_duration() to write the CMD_DURATION environment variable.

The value in the var is pretty-printed using tiered rounding already, so it’s ready to echo as a string in your prompt. For example, for commands that take between 10 seconds and 1 minute:

swprintf(buf, 16, L"%lu.%01us", secs, usecs / 100000);

Which produces output like this, running a rake spec: