How to ignore program's output when using /usr/bin/time?
I want to know how long a program running, so I tried "/usr/bin/time ./program > /dev/null". But soon I found it displays program's output to stderr. I tried "/usr/bin/time ./program > /dev/null 2>&1" then, but /usr/bin/time's output not appear. So my question is, how to ignore program's output, and keep time's output.
Thanks a lot.
Use the -o flag to send the output from time to something else then stderr. For example, if you still want it on screen:
/usr/bin/time -o /dev/tty ./program >/dev/null 2>&1
Or, if you want output on stdout very badly:
/usr/bin/time sh -c './program >/dev/null 2>&1'
or similar. However, now you're also measuring the shell's time to start the process, which may or may not be a problem.