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Remove support for the "command" encoder

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The "command" encoder was mostly intended for use in `%rename` - most
uses can be achieved using the "regex" encoder, so we recommend using
that instead.

The "command" encoder suffers from a number of issues - as the
documentation for it admitted, "[it] is extremely slow compared to all
the other [encoders] as it involves spawning a separate process and
using it for many declarations is not recommended" and that it "should
generally be avoided because of performance considerations".

But it's also not portable.  The design assumes that `/bin/sh` supports
`<<<` but that's a bash-specific feature so it doesn't work on platforms
where `/bin/sh` is not bash - it fails on Debian, Ubuntu and probably
some other Linux distros, plus most non-Linux platforms.  Microsoft
Windows doesn't even have a /bin/sh as standard.

Finally, no escaping of the passed string is done, so it has potential
security issues (though at least with %rename the input is limited to
valid C/C++ symbol names).

Fixes #1806
This commit is contained in:
Olly Betts 2022-02-07 09:47:01 +13:00
commit 467c530e65
6 changed files with 36 additions and 56 deletions
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15
Doc/Manual/SWIG.html
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@ -2064,23 +2064,10 @@ and a more descriptive one, but the two functions are otherwise equivalent:
<tt>%rename("regex:/(\\w+)_(.*)/\\u\\2/")</tt></td>
<td><tt>prefix_print</tt></td><td><tt>Print</tt></td>
</tr>
<tr>
<td><tt>command:cmd</tt></td>
<td>Output of an external command <tt>cmd</tt> with the string passed to
it as input. Notice that this function is extremely slow compared to all
the other ones as it involves spawning a separate process and using it for
many declarations is not recommended. The <i>cmd</i> is not enclosed in
square brackets but must be terminated with a triple <tt>'&lt;'</tt> sign,
e.g. <tt>%rename("command:tr&nbsp;-d&nbsp;aeiou &lt;&lt;&lt;")</tt>
(nonsensical example removing all vowels)</td>
<td><tt>Print</tt></td><td><tt>Prnt</tt></td>
</tr>
</table>
<p>
The most general function of all of the above ones (not counting
<tt>command</tt> which is even more powerful in principle but which should
generally be avoided because of performance considerations) is the
The most general function of all of the above ones is the
<tt>regex</tt> one. Here are some more examples of its use:
</p>