man bash と info 探してみたましたが、 %(...)T 以外はまだ用途ないみたいです。

```
       printf [-v var] format [arguments]
              Write  the formatted arguments to the standard output
under the control of the format.  The -v option causes the output to
be assigned to
              the variable var rather than being printed to the standard output.

              The format is a character string which contains three
types of objects: plain characters, which are simply  copied  to
standard  output,
              character escape sequences, which are converted and
copied to the standard output, and format specifications, each of
which causes print-
              ing of the next successive argument.  In addition to the
standard printf(1) format specifications, printf interprets the
following exten-
              sions:
              %b     causes printf to expand backslash escape
sequences in the corresponding argument (except that \c terminates
output, backslashes in
                     \', \", and \? are not removed, and octal escapes
beginning with \0 may contain up to four digits).
              %q     causes printf to output the corresponding
argument in a format that can be reused as shell input.
              %(datefmt)T
                     causes printf to output the date-time string
resulting from using datefmt as a format string for strftime(3).   The
 corresponding
                     argument is an integer representing the number of
seconds since the epoch.  Two special argument values may be used: -1
represents
                     the current time, and -2 represents the time the
shell was invoked.  If no argument is specified, conversion behaves as
if -1  had
                     been given.  This is an exception to the usual
printf behavior.

              Arguments  to  non-string  format  specifiers are
treated as C constants, except that a leading plus or minus sign is
allowed, and if the
              leading character is a single or double quote, the value
is the ASCII value of the following character.

              The format is reused as necessary to consume all of the
arguments.  If the format requires more arguments than are  supplied,
the  extra
              format  specifications behave as if a zero value or null
string, as appropriate, had been supplied.  The return value is zero
on success,
              non-zero on failure.
```

2015年5月4日 14:01 Nobuyoshi Nakada <nobu / ruby-lang.org>:
>
>
> 2015年5月4日月曜日、Tanaka Akira<akr / fsij.org>さんは書きました:
>>
>> bash の printf で、%(DATEFMT)T という例はあるようです。
>>
>> $ printf '%(%F %T %z)T\n' 946652400
>> 2000-01-01 00:00:00 +0900
>
>
> なるほど。ところで%(...)はT以外でも使えるのでしょうか。