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Date: Thu, 04 Dec 2003 15:51:09 +0530
From: Raj <raju@mailandnews.com>
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To: fengxj <fengxiangjun@neusoft.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: system() return different value under 2.4.23 and 2.6.0-test11
References: <00b801c3ba23$a3115670$1801010a@fengxj>
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fengxj wrote:

>-----------------------------
>#include <stdio.h>
>#include <stdlib.h>
>#include <signal.h>
>
>int main(void)
>{
>        int ret;
>
>        signal(SIGCHLD, SIG_IGN);
>
>        ret = system("/bin/date 1>/dev/null");
>        printf("%d\n", ret);
>
>        return 0;
>}
>----------------------------
>
>runs under 2.4.23 with ret = 0,
>but under 2.6.0-test11, ret = -1.
>
>Why?
>
>And when i remove 
>    signal(...)
>it returns the same value 0. 
>  
>

It's happening because of the return values of wait4(). wait4() is
returning -1 in test11 whene SIGCHLD is SIG_IGN'ed.
/Raj