The binary for readlink is located in /bin.
The usage text as it appears in iOS 4.2.1:
Usage: readlink [OPTION]... FILE Print value of a symbolic link or canonical file name -f, --canonicalize canonicalize by following every symlink in every component of the given name recursively; all but the last component must exist -e, --canonicalize-existing canonicalize by following every symlink in every component of the given name recursively, all components must exist -m, --canonicalize-missing canonicalize by following every symlink in every component of the given name recursively, without requirements on components existence -n, --no-newline do not output the trailing newline -q, --quiet, -s, --silent suppress most error messages -v, --verbose report error messages --help display this help and exit --version output version information and exit Report readlink bugs to firstname.lastname@example.org GNU coreutils home page: <http://www.gnu.org/software/coreutils/> General help using GNU software: <http://www.gnu.org/gethelp/> Report readlink translation bugs to <http://translationproject.org/team/> For complete documentation, run: info coreutils 'readlink invocation'
This command does not need to be run as root. Mobile will do fine.