Duration between two time stamps

[hancooper]

‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
On Thursday, August 19, 2021 2:47 PM, Chet Ramey <chet.ramey@case.edu> wrote:

> On 8/19/21 1:10 AM, Tapani Tarvainen wrote:
>
> > Incidentally, why does ${var:offset} with a negative offset result in
> > an empty string when the variable is shorter than the offset? E.g.,
> > x=abc
> > echo ${x: -6}
> > I find that counterintuitive,
>
> Why? It's an out-of-bounds error.
>
> > and it'd actually be useful to
> > be able to get "at most N characters from the end".
>
> If you want that, you can use ${#x} to get the length and work from there.

Why does the following EPOCHREALTIME computation not work ?

ta=$( $EPOCHREALTIME | tr ',' '.' )
grep ...
tb=$( $EPOCHREALTIME | tr ',' '.' )
dt=$( ${tb}-${ta} | bc )
printf '%s\n' "ta:$ta | tb:$tb | dt: $dt"

Thank you