PHP exec（）和运行shell脚本给出了不同的结果

Question

I have script.sh that sends a request to some URL and prints the execution time using whet. Here is the source code:

time wget http://some.url

When I run it from command line, I see time result with an accuracy of 3 decimal places:

real    0m0.584s
user    0m0.000s
sys     0m0.002s

But, when I run this SH using PHP function exec("script.sh", $output) - , I see time result with an accuracy of only 2 decimal places:

0.00user 0.00system 0:00.32elapsed 0%CPU (0avgtext+0avgdata 3788maxresident)k

How can I get the same result, as I do see in command line?

Answer 1

The answer is in the manual:

Note: some shells (e.g., bash(1)) have a built-in time command that provides less functionality than the command described here. To access the real command, you may need to specify its pathname (something like /usr/bin/time).

You're getting the increased precision from the bash builtin; if you run /usr/bin/time from the shell you will see two decimal places as well.

Unfortunately, time is a special case, in that it's a keyword and not actually a builtin command. Otherwise bash's builtin command could be used to force it.

So it looks like you're stuck with two decimal places unless you want to try a different method:

start_time=`date +%s%N`
wget http://some.url
end_time=`date +%s%N`
bc -l <<< "scale=4;($end_time - $start_time) / 1000000000"