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From: rsh@hpfcdc.HP.COM (Scott Holbrook)
Newsgroups: comp.sys.hp
Subject: Re: The "getdtablesize" command
Message-ID: <5570555@hpfcdc.HP.COM>
Date: 21 Dec 90 18:11:21 GMT
References: <28687@mimsy.umd.edu>
Organization: HP Fort Collins, Co.
Lines: 45

>>   Try:
>>
>>   #include <sys/types.h>
>>
>>   #ifdef hpux
>>       t = FD_SETSIZE;
>>   #else /* hpux */
>>       t = getdtablesize();
>>   #endif /* hpux */

> Art Harkin
> Hewlett Packard

> How come that _no_one_ in the world, not even HP, uses its own system
> call to do this ? (sysconf, a solution with which I posted a few days
> ago).

The sysconf() solution is the preferred method.  However, the submitter
stated that he was running on a HP-UX 3.1 system, which did not support
the sysconf(_SC_OPEN_MAX) call.  So, your proposed solution wouldn't
have worked for the author of the basenote.

Here is another possible solution that should work properly on all
HP-UX releases (and probably on other systems as well):

#include <stdio.h>
#include <unistd.h>

int
getdtablesize()
{
#ifdef _SC_OPEN_MAX
    return sysconf(_SC_OPEN_MAX);
#else
    return _NFILE;
#endif
}

A better solution is to modify your source code to call sysconf()
directly.  sysconf() is part of the POSIX 1003.1 standard, so should
be the most portable solution.  getdtablesize() is a BSDism, so will
probably only be available on BSD or BSD derived systems.

Scott Holbrook / rsh@hpfcla.fc.hp.com
HP-UX kernel/commands