linux show process duration

how do I show how long it takes to run a command on linux? eg

gunzip large.gz

and I want 开发者_开发百科to show how long it took.

In bash, $ time gunzip large.gz will tell you how long $ gunzip large.gz takes.

You can also watch the process while it's executing using top or ps.

Although one can always use $ time (command), I prefer using the method which would spit out the time even when the process is running. To do that, there is one simple way:

$ ps -p ?? -o etime

Where ?? is the pid of the running process. This will give the exact time elapsed since the start of the process.