Memory fault(coredump) while using Environment variables

Applications Programming
1

Hi,

Actually I am facing one issue while using the getenv() in the C/C++ program.

I want to take the file path from environment variables and if am not defining the environment path, its showing the message like this�!

Memory fault(coredump)

Actually I want to handle the error , when I am not defining the enviornment path.

Eg:code:

char *LOG_FILE = getenv("LOG_PATH");
FILE * pFile = fopen(LOG_FILE,"a");
int main ()
{
    char name [100];
    gets (name);
    fprintf (pFile,"\nName %s�,name);
    return 0;
}

If am getting the enviornment path locally rather than in the program mentioned above, then its working fine.But I have to use it globally.

Can anybody help me out in this?

Thanks in Advance...!

2

This code must be C++, since you cannot declare global variables from function return values in C. This bug is why I think that feature was a bad idea... fopen(getenv("LOG_PATH"),"a"); might work but will crash if LOG_PATH is not set, and you should be calling getenv and fopen in main instead anyway, or at least from a function which knows the proper order to set them in, which the compiler doesn't.

3

You can declare and initialize variables globally but it will crash if the env variable LOG_PATH is not set and make sure that the proper header files are included...

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

char *LOG_FILE = getenv("LOG_PATH");
FILE *pFile = fopen(LOG_FILE, "a");

int main()
{
    char name[100];
    gets(name);
    fprintf (pFile,"\nName %s", name);
    return 0;
}
4

Only C++ lets you initialize global variables from function return values, and I don't think it guarantees what order they're set in -- it could call fopen before getenv gets called. C only lets you initialize them from constant values.

5

Yes I should have pointed out that this is only possible with a C++ compiler...C compilers don't understand global variable initializations using functions. So you can write in C but compile with a C++ compiler if that makes sense.

6 
char *LOG_FILE = NULL;
FILE * pFile =  NULL;

int main ()
{
    char name [100]={0x0};
    LOG_FILE=getenv("LOG_FILE");
    pfile = fopen(LOG_FILE,"a");
    gets (name);
    if(pfile!=NULL)
        fprintf (pFile,"\nName %s�,name);
    return 0;
}

both pfile and LOG_FILE are now global.

7

Well I think jim mcnamara's solution is the best one.