问题:

I gone thro many websites,all provided the same info that we cannot access call_history.db My question is that can we change the access mode for that db using system('chmod 777 /db path/') command ??

回答1:

You can't, at least on a non-jailbroken phone.

回答2:

App store apps run in a sandbox. You don't have read/write permission to modify those directories from any app running in its sandbox.

回答3:

why would you want to a have the information of the call list? also why would you want it to change to such liberal permissions?

you don't have root access on the (non-jailbroken)device, and if you find a way of escalating to root privelages, what are the chances of apple allowing it on the appstore?