is there a simple way to change the default value of a file size shown from byte to megabyte when calling commands like wc -c; ls -l; du; etc.
BTW i'm running FreeBSD (OS X)
du -m
wc # no but you can do the division yourself
man ls # don't have access to a OS X system at the moment but there should be an option.
The GNU coreutils have the BLOCK_SIZE variable, but given you're on BSD, I suppose you're only option is to use -h (human readable) option with ls and du and, of course, the output will not exactly match your requirement.
I believe that wc's -c means explicitly bytes and its output is not affected by the value of the BLOCK_SIZE variable even on GNU systems.
P.S. Just read the above post, yes, du may have the appropriate option.