How to pull the apks from my android phone I have a rooted android phone. I am trying to pull the applications from /system/app/. However this simply does not copy the apk. What I have tried.

    adb shell
    su
    cd data
    cd app
    ls


A lot of applications are shown. However when I try to pull it it says 

adb pull /data/app test

pull: building file list...
0 files pulled. 0 files skipped.


When I try to pull it from the system/app it pulls it but no file is created on my computer. I have specified the file name, tried with it and without it. Could someone please tell me what I am doing wrong?

I have also tried it individually with specific apks. But that doesnt work either.
If you're using su to get root privileges when you shell in (which you've indicated you are) then that means you're not root on the shell by default. adb pull fails with that error message because it doesn't have permission to index the directory and pull the contents.

You should be able to restart adb on your device with adb root first:

adb root
adb pull /data/app/


And a fully illustrative example to show that this is the likely issue (I used /data/misc just because it's smaller):

[09:27:23] ~/adb-test $ adb pull /data/misc/
pull: building file list...
0 files pulled. 0 files skipped.  &lt;-------------- Same issue because we're not root yet!
[09:27:49] ~/adb-test $ adb root
[09:27:56] ~/adb-test $ adb pull /data/misc/
pull: building file list...
... Snip all of the individual files here ...
24 files pulled. 0 files skipped.
65 KB/s (7732 bytes in 0.115s)
[09:27:59] ~/adb-test $




Another option for restarting adb as root is Chainfire's adbd insecure app. Some ROMs will not support the adb root command, though, as they were not built to allow it. This will be true if you root a stock ROM without installing a custom one, for example.