Just wrote a simple program to use NSProcessInfo to dump the environment variables on my iPhone. And I found the iPhone running my app standalone predefines the following environment variables:
SHELL = /bin/sh CFFIXED_USER_HOME = /private/var/mobile/Applications/[UUID] PATH = /usr/bin:/bin:/user/sbin:/sbin TMPDIR = /private/var/mobile/Applications/[UUID]/tmp __CF_USER_TEXT_ENCODING = 0x1F5:0:0 USER = mobile LOGNAME = mobile HOME = /private/var/mobile/Applications/[UUID]
The [UUID] is the UUID for your application, to differentiate the directory for your application from the directory used by other applications.
I find it interesting because it means that if you have some Unix C code that attempts (for example) to find the location of a file without using the various search methods available in iOS Cocoa, you can do it. For example, you can change the working directory to the documents folder by writing:
(The standard iPhone directories are documented here: The Application Runtime Environment, under “The File System”.)
That can be quite useful…