[lug] question about ext 2/3 fs

[D. Stimits]

Paul E Condon wrote:

>I'm having a problem with mtime handling in coreutils. I won't
>give details of that problem, but ...
>
>I look into how Linux keeps track of mtime for files. I find
>that it is stored in the inode of the file, and that 64 bits are
>allocated for the number of seconds since the Unix epoch.
>Fine but somehow 'ls --full-time' displays a fractional part of
>a second right down to a nanosecond (9digits!). Where is this
>stored? It haven't seen any mention of it. Where is the way
>its done documented?
>  
>
I won't guarantee it, but I highly doubt it is *stored* to that 
resolution. Several of the UNIX type time functions and structures 
reserve that high of a resolution so it is possible to use that much, 
but the input those functions use will not necessarily be that high of a 
resolution. Garbage in, garbage out, i.e., I believe that the functions 
used do not actually measure the resolution of the raw data, and by 
default, just report all that might have been used. I notice on mine, 
for example, that almost all of the time given is padded to zero, 
despite showing more decimals. If it does not pad right-most decimals, 
it's probably a bug/oversight.

D. Stimits, stimits AT comcast DOT net