D. Hazelton wrote:
>>I would need to write a compiled C program to do all
>>sorts of fragile hackish things like calling a script
>>/sbin/init.sh.
>
>
> Problem is, the program
> would not be fragile or hackish - it'd be almost as simple as a
> "hello world" program.
>
> #include <unistd.h>
>
> int main() {
> /* if this fails the system is busted anyway */
> return execve( "/bin/sh", "/sbin/init.sh", 0 );
> };
This attempt nicely illustrates Kyle's point. This program *is*
fragile and hackish. It is fragile because, even though it is only
five lines, contains two major bugs:
1. execve takes an argv array, not a null-terminated list of
strings. So this compiles with a warning about incompatible
pointer types; you meant to use execl(3).
2. In the exec family, the path to the program is different from
argv[0]. So the correct line would be
return execl("/bin/sh", "sh", /sbin/init.sh", 0);
It is hackisch, because it also lacks a feature commonly
found in such wrappers:
3. arguments passed to the wrapper are not forwarded to the
executable. In particular, init takes several arguments
(e.g. the runlevel), which should be forwarded to the
final executable.
Just try completing the wrapper on your own.
Regards,
Martin
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