asterisk users - Jul 2008 - Explication for ast_safe_system

Can someone please explain the reason on the following code (in
asterisk.c, function ast_safe_system()):

/* Close file descriptors and launch system command */
for (x = STDERR_FILENO + 1; x < 4096; x++)
    close(x);


Why to close so many descriptors?

Thanks in advance
?ric

On Saturday 19 July 2008 06:41:04 Eric Dantie wrote:
> Can someone please explain the reason on the following code (in
> asterisk.c, function ast_safe_system()):
>
> /* Close file descriptors and launch system command */
> for (x = STDERR_FILENO + 1; x < 4096; x++)
>     close(x);
>
>
> Why to close so many descriptors?
There's no way to know how many file descriptors are actually open, and
every
file descriptor that is open when a process is forked is duplicated in the new
process.  Also, if the process being forked is long running (such as an AGI),
then there could be side effects to not closing all descriptors in a child
process (such as receiving a SIGPIPE when the other end closes).

Eventually, we could probably start registering the highest file descriptor to
a central function, ensuring that we close all of them.  It is admittedly a
hack to pick an arbitrary number like this.

-- 
Tilghman

Never noticed the c is next to the n, however thinking about it, the c
is to the f what the n is to the j. which might make for an easy
mistake. I guess if you put only your right hand on the keyboard, and
mistake the f for the j on your right index finger that it could
happen easyly.


On Sat, Jul 19, 2008 at 7:41 AM, Eric Dantie <edantie at gmail.com>
wrote:
> Can someone please explain the reason on the following code (in
> asterisk.c, function ast_safe_system()):
>
> /* Close file descriptors and launch system command */
> for (x = STDERR_FILENO + 1; x < 4096; x++)
>    close(x);
>
>
> Why to close so many descriptors?
>
> Thanks in advance
> ?ric
>
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