simple problem

[J Wang]

the c code as follows:

#include <stdio.h>
#include <stdlib.h>

int main()
{
printf("%s\n", getenv("NAME")) ;
return 0;
}

Segmentation Fault

why?

cheers,

[Leor Zolman]

Re: simple problem

On Fri, 9 Apr 2004 23:51:26 GMT, J Wang <csmjbw@bath.ac .uk> wrote:
[color=blue]
>
>the c code as follows:
>
>#include <stdio.h>
>#include <stdlib.h>
>
>int main()
>{
> printf("%s\n", getenv("NAME")) ;
> return 0;
>}
>
>Segmentation Fault
>
>why?[/color]

NULL.
-leor
[color=blue]
>
>cheers,[/color]


--
Leor Zolman --- BD Software --- www.bdsoft.com
On-Site Training in C/C++, Java, Perl and Unix
C++ users: Download BD Software's free STL Error Message Decryptor at:

https://www.bdsoft.com/tools/stlfilt.html

[Mike Wahler]

Re: simple problem

"J Wang" <csmjbw@bath.ac .uk> wrote in message
news:Pine.GSO.4 .44.04041000381 90.13163-100000@amos.bat h.ac.uk...[color=blue]
>
> the c code as follows:
>
> #include <stdio.h>
> #include <stdlib.h>
>
> int main()
> {[/color]

char *name = getenv("NAME");
[color=blue]
> printf("%s\n", getenv("NAME")) ;[/color]

if(name)
printf("%s\n", name);
else
printf("%s\n", "getenv() returned NULL");
[color=blue]
> return 0;
> }
>
> Segmentation Fault
>
> why?[/color]

Most likely you tried to dereference a NULL pointer.

*Always* check the return value of a function
which can fail.

-Mike

[Martin Ambuhl]

Re: simple problem

J Wang wrote:
[color=blue]
> the c code as follows:
>
> #include <stdio.h>
> #include <stdlib.h>
>
> int main()
> {
> printf("%s\n", getenv("NAME")) ;
> return 0;
> }
>
> Segmentation Fault
>
> why?
>[/color]

Perhaps "NAME" is not defined in the environment, so getenv() returns
NULL and your attempt to dereference it is illegal. We just had this a
couple of days ago. That you did not see it shows that you violated
usenet etiqutte by posting without following the newsgroup first. You
probably didn't check the FAQ either.

[Barry Schwarz]

Re: simple problem

On Fri, 9 Apr 2004 23:51:26 GMT, J Wang <csmjbw@bath.ac .uk> wrote:
[color=blue]
>
>the c code as follows:
>
>#include <stdio.h>
>#include <stdlib.h>
>
>int main()
>{
> printf("%s\n", getenv("NAME")) ;
> return 0;
>}
>
>Segmentation Fault
>
>why?
>[/color]

getenv is allowed to return NULL. You need to check for that
situation before dereferencing the return value.


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