🚀 go-pugleaf

I've figured out HOW the problem occurs, i just dont know WHY it occurs, or
WHY it should occur. Possibly a bug in the c libs or gcc??
The HOW is: when you putenv() an array, and then modify the array afterwards,
the environment automatically gets changed without executing another
putenv()! This, to me, sounds ludicrous. Even setting the array below to
static char doesn't help.
Sample program:

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

int main(void) {
char timebuf[256];

strcpy(timebuf,"TZ=:/home/flirt/ncohafmuta/tzinfo/US/Central");
printf("Setting TZ to: %s\n",timebuf);
putenv(timebuf);
tzset();
printf("TZ is: %s\n",(char *)getenv("TZ"));
strcpy(timebuf,"TZ=hi");
printf("Redefined timebuf to: %s\n",timebuf);
printf("TZ is: %s\n",(char *)getenv("TZ"));
return 1;
}



-Tony
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Anthony J. Biacco                       Network Administrator/Engineer
admin@intergrafix.net                    Intergrafix Internet Services

    "Dream as if you'll live forever, live as if you'll die today"
http://cygnus.ncohafmuta.com                http://www.intergrafix.net
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In comp.unix.programmer admin@intergrafix.net wrote:
> Hi,

> I write this chat program in C. The platform is linux. The libraries are
> libc 5.4.46-2 and glibc 2.1.3-6, on 2 different machines.

> At the start of the program i have code to set the timezone up to whatever is
> specified in a #define called TZONE, such as "US/Pacific"

> the function i made to accomplish this is:

> void do_timeset(void) {
> char wcd1[266];

> getcwd(wcd1,256);
> /* subdirectory under the absolute cwd where zonefiles are kept */
> /* we dont use the machines own zoneinfo files */
> strcat(wcd1,"/tzinfo");
> sprintf(mess,"TZ=:%s/%s",wcd1,TZONE);
> putenv(mess);
> tzset();
> }

> this works fine. when i do a time(&tm); and then output a ctime(&tm);
> it prints out the current time for the zone.

> however, after a few lines of simple code, and then printing out the time
> again, it reverts back to local machine time! but only on glibc, on the libc5
> it still prints out the right time for the zone.
> after checking the environment, i've noticed that after a line of code, the 
> TZ variable just disappears! it disppearrs on both the libc5 and the glibc,
> but only the glibc makes it take effect as previously stated.

> why the TZ varaible gets lost, i have no clue. it doesn't matter what the
> code line is that makes it get lost either..for example..if i have the code:

> do_timeset();
> system("env");
> time(&tm);
> printf("%s",ctime(&tm));
> mess[0]=0;
> system("env");
> time(&tm);
> printf("%s",ctime(&tm));
> somevariable=1;
> system("env");
> time(&tm);
> printf("%s",ctime(&tm));

> the first env will be correct, the second and third ctime() will be missing
> the TZ. if i comment out the mess[0]=0; then the first and second ctime()
> will be right and the third ctime will be wrong (as a result of the code
> somevariable=1;) btw, mess is a global char of size 9600
> if i redo the do_timeset() after all that, it will come back to the current
> time, but then on the very next line of code it will revert.

> i've written a small sample problem and could not get the problem to
> reproduce there. so i assume it's something in my programming, i'd just like
> to know what the heck I could be coding wrongly that would cause this
> to happen! :( Or even what concepts would cause this to happen.

> lastly i'd like to add, relevantly maybe, that i'm not doing anything like
> forking, or any kind of system calls besides the debugging ones listed above.

> Any help would be appriecated,

> -Tony
> .-._.-._.-._.-._.-._.-._.-._.-._.-._.-._.-._.-._.-._.-._.-._.-._.-._.-.
> Anthony J. Biacco                       Network Administrator/Engineer
> admin@intergrafix.net                    Intergrafix Internet Services

>     "Dream as if you'll live forever, live as if you'll die today"
> http://cygnus.ncohafmuta.com                http://www.intergrafix.net
> .-._.-._.-._.-._.-._.-._.-._.-._.-._.-._.-._.-._.-._.-._.-._.-._.-._.-.


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Anthony J. Biacco                       Network Administrator/Engineer
admin@intergrafix.net                    Intergrafix Internet Services

    "Dream as if you'll live forever, live as if you'll die today"
http://cygnus.ncohafmuta.com                http://www.intergrafix.net
.-._.-._.-._.-._.-._.-._.-._.-._.-._.-._.-._.-._.-._.-._.-._.-._.-._.-.