List files with timestamp since epoch

If you have GNU find, you can do it entirely using find:

find / -printf '%p %C@\n'

The format specifiers are:

     %p     File's name.
     %Ck    File's last status change time in the format specified by
            k, which is the same as for %A.
     %Ak    File's last access time in the  format  specified  by  k,
            which  is  either `@' or a directive for the C `strftime'
            function.  The possible values for k  are  listed  below;
            some  of  them might not be available on all systems, due
             to differences in `strftime' between systems.

             @      seconds  since  Jan.  1,  1970,  00:00  GMT,  with
                    fractional part.

If you don't want fractional parts, use s instead of @ as the time format specifier. (There are a few systems without s, but Linux and *BSD/OSX do have s.)

find / -printf '%p %Cs\n'

why don't you ask find to stat for you ?

find / -exec stat -c'%n %Z' {} +

find will run stat of every entry (file or directory).