strftime Codes for awslogs-datetime-format and awslogs-multiline-pattern Option

3rd chunk of `content/manuals/engine/logging/drivers/awslogs.md`

85a1d682c9ec461eeabd55acb2df81f044ab64eb8e81bdb50000000100000c51

[May 01, 2017 19:00:01] A message was logged
[May 01, 2017 19:00:04] Another multi-line message was logged
Some random message
with some random words
[May 01, 2017 19:01:32] Another message was logged
```

The format can be expressed as a `strftime` expression of
`[%b %d, %Y %H:%M:%S]`, and the `awslogs-datetime-format` value can be set to
that expression:

```console
$ docker run \
    --log-driver=awslogs \
    --log-opt awslogs-region=us-east-1 \
    --log-opt awslogs-group=myLogGroup \
    --log-opt awslogs-datetime-format='\[%b %d, %Y %H:%M:%S\]' \
    ...
```

This parses the logs into the following CloudWatch log events:

```console
# First event
[May 01, 2017 19:00:01] A message was logged

# Second event
[May 01, 2017 19:00:04] Another multi-line message was logged
Some random message
with some random words

# Third event
[May 01, 2017 19:01:32] Another message was logged
```

The following `strftime` codes are supported:

| Code | Meaning                                                          | Example  |
| :--- | :--------------------------------------------------------------- | :------- |
| `%a` | Weekday abbreviated name.                                        | Mon      |
| `%A` | Weekday full name.                                               | Monday   |
| `%w` | Weekday as a decimal number where 0 is Sunday and 6 is Saturday. | 0        |
| `%d` | Day of the month as a zero-padded decimal number.                | 08       |
| `%b` | Month abbreviated name.                                          | Feb      |
| `%B` | Month full name.                                                 | February |
| `%m` | Month as a zero-padded decimal number.                           | 02       |
| `%Y` | Year with century as a decimal number.                           | 2008     |
| `%y` | Year without century as a zero-padded decimal number.            | 08       |
| `%H` | Hour (24-hour clock) as a zero-padded decimal number.            | 19       |
| `%I` | Hour (12-hour clock) as a zero-padded decimal number.            | 07       |
| `%p` | AM or PM.                                                        | AM       |
| `%M` | Minute as a zero-padded decimal number.                          | 57       |
| `%S` | Second as a zero-padded decimal number.                          | 04       |
| `%L` | Milliseconds as a zero-padded decimal number.                    | .123     |
| `%f` | Microseconds as a zero-padded decimal number.                    | 000345   |
| `%z` | UTC offset in the form +HHMM or -HHMM.                           | +1300    |
| `%Z` | Time zone name.                                                  | PST      |
| `%j` | Day of the year as a zero-padded decimal number.                 | 363      |

### awslogs-multiline-pattern

The `awslogs-multiline-pattern` option defines a multi-line start pattern using a
regular expression. A log message consists of a line that matches the pattern
and any following lines that don't match the pattern. Thus the matched line is
the delimiter between log messages.

This option is ignored if `awslogs-datetime-format` is also configured.

Title: strftime Codes for awslogs-datetime-format and awslogs-multiline-pattern Option

Summary

This section provides a table of supported `strftime` codes for the `awslogs-datetime-format` option, detailing the meaning and an example for each code. It also briefly introduces the `awslogs-multiline-pattern` option, which allows defining a multi-line start pattern using a regular expression but is ignored if `awslogs-datetime-format` is configured.