What does the (!) mean after uptime on htop

htop author here. Yes, as others already mentioned, it indeed shows up after 100 days of uptime.

The reason is nothing fancy, it's just an Easter egg in the software. Consider that the program is impressed with your uptime, and take it as you will. :)

From htop source code, file UptimeMeter.c, you can see:

char daysbuf[15];
if (days > 100) {
   sprintf(daysbuf, "%d days(!), ", days);
} else if (days > 1) {
   sprintf(daysbuf, "%d days, ", days);
} else if (days == 1) {
   sprintf(daysbuf, "1 day, ");
} else {
   daysbuf[0] = '\0';
}

I think ! here is just a mark that server has been up for more than 100 days.

Reference

• http://sourceforge.net/p/htop/mailman/htop-general/?viewmonth=200707

htop shows the exclamation mark when the server has been up since 100 or more days.

While once system administrators had pride in showing long uptimes, nowadays the system has to be rebooted to be kept up to date with new kernels and some security fixes. For such reason, a long uptime is probably not a good thing and I tend to interpret the exclamation mark as a warning sign.