Let's accept "µs" as alternative time unit for microseconds. We already accept
"us" and "usec" for them, lets extend on this and accept the proper scientific
unit specification too.
We will never output this as time unit, but it's fine to accept it, after all
we are pretty permissive with time units already.
This patch improves parsing and generation of timestamps and calendar
specifications in two ways:
- The week day is now always printed in the abbreviated English form, instead
of the locale's setting. This makes sure we can always parse the week day
again, even if the locale is changed. Given that we don't follow locale
settings for printing timestamps in any other way either (for example, we
always use 24h syntax in order to make uniform parsing possible), it only
makes sense to also stick to a generic, non-localized form for the timestamp,
too.
- When parsing a timestamp, the local timezone (in its DST or non-DST name)
may be specified, in addition to "UTC". Other timezones are still not
supported however (not because we wouldn't want to, but mostly because libc
offers no nice API for that). In itself this brings no new features, however
it ensures that any locally formatted timestamp's timezone is also parsable
again.
These two changes ensure that the output of format_timestamp() may always be
passed to parse_timestamp() and results in the original input. The related
flavours for usec/UTC also work accordingly. Calendar specifications are
extended in a similar way.
The man page is updated accordingly, in particular this removes the claim that
timestamps systemd prints wouldn't be parsable by systemd. They are now.
The man page previously showed invalid timestamps as examples. This has been
removed, as the man page shouldn't be a unit test, where such negative examples
would be useful. The man page also no longer mentions the names of internal
functions, such as format_timestamp_us() or UNIX error codes such as EINVAL.
Throughout the tree there's spurious use of spaces separating ++ and --
operators from their respective operands. Make ++ and -- operator
consistent with the majority of existing uses; discard the spaces.
This is useful if we want to parse RLIMIT_RTTIME values where the common
UNIX syntax is without any units but refers to a non-second unit (µs in
this case), but where we want to allow specification of units.
systemctl would print 'CPUQuotaPerSecUSec=(null)' for no limit. This
does not look right.
Since USEC_INFINITY is one of the valid values, format_timespan()
could return NULL, and we should wrap every use of it in strna() or
similar. But most callers didn't do that, and it seems more robust to
return a string ("infinity") that makes sense most of the time, even
if in some places the result will not be grammatically correct.
Instead of outputting "5h 55s 50ms 3us" we'll now output "5h
55.050003s". Also, while outputting the accuracy is configurable.
Basically we now try use "dot notation" for all time values > 1min. For
>= 1s we use 's' as unit, otherwise for >= 1ms we use 'ms' as unit, and
finally 'us'.
This should give reasonably values in most cases.
