UNIX for Dummies Questions & Answers

I wondered if someone could point out the differences between the time commmand and usr/bin/time and the accuracy one might have over another.

Also, is there a website or two a person could maybe link for me to describe the differences?

Thank you for your time.

/usr/bin/time is an external command. Invoking it causes a fork and an exec to spawn an additional process. The original bourne shell has almost no built-in commands. Today's shells tend to have a lot of built-in commands. This makes them more efficient. Almost all shells have a built-in time command, but the features vary by shell. The built-in time command is more efficient. Also, what if you want to time a built-in command? The external /usr/bin/time cannot do that. Once you have some built-in commands, you really are forced into needing a built-in time to go with them.

In ksh "time" is a compound command which basicly means it can be applied to pipelines easily. Here is a contrived example. It doesn't make sense to pipe stuff to a sleep process, but it's clear that sleep must take some time. So may example is:
grep root /etc/passwd | sleep 2
I'll time that both ways:
$ /usr/bin/time grep root /etc/passwd | sleep 2

real 0.0
user 0.0
sys 0.0
$ time grep root /etc/passwd | sleep 2

real 0m2.04s
user 0m0.01s
sys 0m0.04s
$

The first case was equivalent to:
{ /usr/bin/time grep root /etc/passwd ; } | sleep 2
while the 2nd was equivalent to:
/usr/bin/time { grep root /etc/passwd | sleep 2 ; }

these cases that u have mentioned , i jus wanted to know the reason , y these external and built in comamands behaved differently ..
can u throw some lite ..
n also the command that u have mentioned gives a diffrent result:


[user@acer65 ~]$ /usr/bin/time grep root /etc/passwd
root:x:0:0:root:/root:/bin/bash
operator:x:11:0: operator:/root:/sbin/nologin
0.00user 0.00system 0:00.00elapsed ?%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+201minor)pagefaults 0swaps



wt does "0.00user 0.00system 0:00.00elapsed ?%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+201minor)pagefaults 0swaps "output signify ?????