A small documentation suggestion

[Keith Thompson]

Bash 5.0 adds $EPOCHSECONDS and $EPOCHREALTIME.

The latter expands, each time it's referenced, to the number of
seconds since the epoch with microsecond precision.

Experiment shows that the expansion always has exactly 6 digits after
the decimal point.  For example, if you typed "echo $EPOCHREALTIME"
at just the right moment, it might print "1546925845.000000", not
"1546925845.0" or "1546925845".

I suggest documenting this behavior. It would be nice to be able to
depend on the exact format, for example that ${EPOCHREALTIME/*./}
is always exactly 6 digits long.

(The number of digits before the decimal point won't change until 2286;
I'm not too worried about that.)

Proposed patch for doc/bashref.texi (please tweak this if needed):

diff --git doc/bashref.texi doc/bashref.texi
index d33cd571..6381c61a 100644
--- doc/bashref.texi
+++ doc/bashref.texi
@@ -5911,6 +5911,7 @@ Similar to @code{BASH_ENV}; used when the shell
is invoked in
 @item EPOCHREALTIME
 Each time this parameter is referenced, it expands to the number of seconds
 since the Unix Epoch as a floating point value with micro-second granularity
+as if formatted using a @samp{"%.6f"} @code{printf} format
 (see the documentation for the C library function @var{time} for the
 definition of Epoch).
 Assignments to @env{EPOCHREALTIME} are ignored.
@@ -5918,7 +5919,7 @@ If @env{EPOCHREALTIME} is unset, it loses its
special properties, even if
 it is subsequently reset.

 @item EPOCHSECONDS
-Each time this parameter is referenced, it expands to the number of seconds
+Each time this parameter is referenced, it expands to the integer
number of seconds
 since the Unix Epoch (see the documentation for the C library function
 @var{time} for the definition of Epoch).
 Assignments to @env{EPOCHSECONDS} are ignored.

    -- Keith Thompson