Where does `time` output its result?

Question

I'm on Ubuntu.

Running time seems to output its result to something other than STDOUT or STDERR. Here's why I think so:

[siminm@amide ~]$ time echo hi
hi

real    0m0.000s
user    0m0.000s
sys 0m0.000s
[siminm@amide ~]$ time echo hi >/dev/null 

real    0m0.000s
user    0m0.000s
sys 0m0.000s
[siminm@amide ~]$ time echo hi 2>/dev/null 
hi

real    0m0.000s
user    0m0.000s
sys 0m0.000s
[siminm@amide ~]$ time echo hi 2>&1 >/dev/null 

real    0m0.000s
user    0m0.000s
sys 0m0.000s
[siminm@amide ~]$ time echo hi &>/dev/null 

real    0m0.000s
user    0m0.000s
sys 0m0.000s

HOWEVER

[siminm@amide ~]$ /usr/bin/time echo hi 2>/dev/null 
hi

Answer 1

Your shell, which is probably bash, provides a builtin command time. There is also a separate program called time in /usr/bin/, which is in your $PATH. The behavior of the two is different. If you want consistency across all configurations, you should use the program /usr/bin/time instead of the bash builtin time.

Answer 2

You are always only redirecting the output of your command. Since time writes to stderr try the following:

(time ls >> /stdout/output/of/ls 2>> /stderr/output/of/ls) 2>> /output/of/time

Answer 3

"time" builtin output goes to what stderr points to before redirections do happen.

Any non builtin command like /usr/bin/time cannot override the redirection as they happen before it is launched so its output goes to stderr.