Sometimes it is interesting to see how long a program took to run. This is usefull to see how long a backup took to be complete, how long you surfed the net, or many other things.
This is taken from one of my posts to a mailing-list I used to subscribe:
stw@laptop:~> date ; echo This line intentionally left blank ; sleep 5 ; date Sa Jun 18 20:47:59 CEST 2005 This line intentionally left blank Sa Jun 18 20:48:04 CEST 2005
which will tell you start and end of the run of the program (tar, netscape, whatever). You have to do the math on your own.
‘time’ does this:
stw@laptop:~> time sleep 5 real 0m5.066s user 0m0.002s sys 0m0.002s
So we know how long the nap really was, and how much time the CPU spent to run the sleep-application. The drawback is that ‘time’ only times one command. So if you want to time pipes or multiple commands that run after each other, you need to put them into a script and time that script, or use ‘date’ and do the math…