how can't I redirect the output of time command

Question

I tried to redirect the output of the time command , but I couldn't

$time ls > filename
real    0m0.000s
user    0m0.000s
sys     0m0.000s

In the file i can get the output of the ls command not the time Please explain me , wny I couldn't and how can I ?

Answer 1

you can redirect the time output using,

(time ls) &> file

Because you need to take (time ls) as a single command so you can use braces.

Answer 2

time is shell builtin and I'm not sure if there is way to redirect it. However you can use /usr/bin/time instead, which definitely accept any output redirections.

Answer 3

The command time sends it's output to STDERR (instead of STDOUT). That's because the command executed with time normally (in this case ls) outputs to STDOUT.

If you want to capture the output of time, then type:

(time ls) 2> filename

That captures only the output of time, but the output of ls goers normal to the console. If you want to capture both in one file, type:

(time ls) &> filename

2> redirects STDERR, &> redirects both.

Answer 4

no need to launch sub shell. Use a code block will do as well.

{ time ls; } 2> out.txt

or

{ time ls > /dev/null 2>&1 ; } 2> out.txt