NetNews Offline 2/NetNews Offline Volume 2.iso/news/comp/lang/c-part1/8264

Text File | 1996-08-05 | 1.6 KB | 43 lines

Path: mail2news.demon.co.uk!genesis.demon.co.uk
From: Lawrence Kirby <[e-mail]>
Newsgroups: comp.lang.c
Subject: Re: system() & error detection
Date: Sat, 02 Mar 96 16:36:25 GMT
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References: <4gt24g$[e-mail]> <[e-mail]>
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In article <[e-mail]>
           [e-mail] "Guus Leeuw jr." writes:

>According to the standard (references are listed with FAQ 19.27),
>system() will return -1 upon execution error. Any other value is the
>return code of the called program.

Not true. The standard only defines the meaning of the return value of system
when its argument is a null pointer (it returns nonzero if a command
processor is available). When the argument is not a null pointer the return
value is entirely implementation-defined. The standard makes no mention of
the value -1.

>The return code of the called program is what you return from main().
>For examples `int main(){ return 1; }. The value 1 is the return code.

This isn't guaranteed in general and isn't true is specific cases such as
Unix.

>The caller of this little program has to know how to interpret the
>returned value.

True. Unfortunately there is no system-independent way of doing this.

--
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Lawrence Kirby | [e-mail]
Wilts, England | [e-mail]
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