Selecting individual processes using top on jailbroken iphone 5 - ios

Question

So I need to print out an individual iphone app's memory usage for a soak test. It would help greatly if there was a stored log monitoring usage against time (ran periodically within the automated test).
To do this I've jailbroken the iPhone and installed mobile terminal. My plan was to use top -p to filter out the rest of the processes and then pipe out the output to a log file. Then the data could be reclaimed at a later date and analysed.
Unfortunately, when I run for PID 616:
top -p 616
then all I get is 616 printed off multiple times:
Processes: 77 total, 1 running, 5 stuck, 71 sleeping... 335 threads 02:38:09
Load Avg: 1.23, 0.93, 0.90 CPU usage: 3.33% user, 0.00% sys, 96.67% idle
SharedLibs: num = 0, resident = 0 code, 0 data, 0 linkedit.
MemRegions: num = 0, resident = 0 + 0 private, 0 shared.
PhysMem: 108M wired, 152M active, 39M inactive, 497M used, 519M free.
VM: 28G + 0 904390(0) pageins, 32065(0) pageouts
PID COMMAND %CPU TIME #TH #PRTS #MREGS RPRVT RSHRD RSIZE VSIZE
616
616
616
616
616
616
616
616
616
616
616
616
616
616
616
616
616
616
I've looked around, and it seems that the flags on the top for iphone are slightly different but I can't find a specific description. Can anyone show me how to print out the data just for one process?
Thanks.

Answer 1

If you want to find out the proper command line switches for top, or anything else, try something like this:
>> top --help
You will see, however, that the PID (-p) switch isn't supported in the version for jailbroken iOS.
However, if you use this:
>> top -l 2 | grep 616
It should give you what you need (in the second line of output). The -l switch gives you N samples. You need at least 2, because top calculates CPU% as a delta between samples, so with only 1 sample, it will always be 0%. If you only need memory usage, though, you can probably use:
>> top -l 1 | grep 616
Using just top | grep 616 doesn't work, because it runs continuously. You probably just want a single value, and then should let top exit.
Note: you'll probably need to install grep from Cydia, also. Just search for grep. It's a package published by Saurik.
Warning: because you're using grep to search for the right PID, you may need to have your code that parses the log file validate its log input. The right output will be in the file, but if the numeric PID matches any other lines, also, you'll get additional data. For example, if the PID you search for also happens to be the number of MB of memory used by another process, you'll get additional lines of output. The first column in your file, however, will always be the PID.