'size' vs 'ls -l' to get the size of an executable file

Question

For the same file, I think the output of ls -l xxx is always greater than or equal to the output of size xxx.

But when I type ls -l /bin/ls the output is:

 -rwxr-xr-x 1 root root 104508  1月 14  2015 /bin/ls

For size /bin/ls, the output is:

   text    data     bss     dec     hex filename
 101298     976    3104  105378   19ba2 /bin/ls

Why is ls showing less than size? 104508 < 105378

Answer 1

ls -l is telling you the size of the file, while the size command tells you the size of the executable image stored in the file -- how much memory it will require when loaded. Some segments (such as .bss) are zero-initialized rather than requiring data in the file to initialize them, so the the file may well be smaller than the executable image as a result.