needle -filter

[Jan T. Kim]

On Tue, Jun 10, 2003 at 11:53:16AM +0100, Peter Rice wrote:
> Jan T. Kim wrote:
> >     needle <file>:abc <file>:xyz
> > 
> > will not work with input streams. Perhaps, such capability could be
> > implemented by defining some special name for the "standard input file"
> > or "standard input database"? I haven't found such a thing in the USA
> > specification, but perhaps, that's already invented?
> 
> There is a special name - stdin - but it can only be opened once.

Ok -- thanks for this pointer, I managed to overlook this. Among general
lack of attention, I overlooked it because I was focusing on something
like a special file name "-", which is generically used in the *nix /
command line world to denote the standard input.

> How many Unix commands do read more than one input stream from stdin?

None. There are no multiple standards in the Unix world, so there is
no multiple stdin...  ;-)

More seriously: The standard input is logically one input stream. The
issue here is not multiple input streams which, in the Unix environment,
would typically be handled by using named pipes (this may also be an
approach for solving the problem from which this thread originated).
In many cases, though, it is preferable to have one input stream which
is structured into multiple records, such as sequence entries in our
case. Handling such multiple-record input would be more convenient if
EMBOSS did not have to perform a pass through an entire stream for each
record it needs to obtain. This approach is restricted to streams which
can be "reproduced", which does not generally apply to the standard
input stream.

Kind regards, Jan
-- 
 +- Jan T. Kim -------------------------------------------------------+
 |    *NEW*    email: kim at inb.uni-luebeck.de                          |
 |    *NEW*    WWW:   http://www.inb.uni-luebeck.de/staff/kim.html    |
 *-----=<  hierarchical systems are for files, not for humans  >=-----*