Re: I have a question...

[emery@goldfinger.mitre.org (David Emery)]

Let me clarify what is going on here, since there appears to be some
confusion.  

The Unix (POSIX) system interface does NOT recognize the "~~
character.  This (like other wildcards, such as "*" and "?") is
processed by the shell (or by a 'friendly' applications program.)

So a call to OPEN (FILENAME => "~/myfile") will not work correctly if
the OPEN procedure does not interpret the "~" character.  This would
be the case for POSIX_IO.OPEN, for instance.

A call to SYSTEM (COMMAND => "~/bin/myprogram ~/myfile") will probably
work correctly, assuming that SYSTEM here is the Unix system command,
which invokes the shell.

What is interesting is a call to TEXT_IO.OPEN (NAME => "~/myfile").
This is interesting because there is no requirement for TEXT_IO to
process wildcards, but it is not 'illegal' for TEXT_IO to do so.  Nor
does the POSIX/Ada standard (IEEE Std 1003.5-1992) say anything about
this (maybe it should...)  As a result, this call to TEXT_IO.OPEN is
clearly implementation-defined, and different Ada compilers on the
same operating system may give different results.

I hope this clarifies the situation.  The bottom line:  "~" is a
wildcard processed by the shell, just as "*" and "?".  Some friendly
applications duplicate the shell processing, but users should not
expect this for 'standard' interfaces such as TEXT_IO and POSIX_IO.

				dave
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