How can I assign to a pointer array like char *args[]; ?

haydari · 04-09-2007, 06:23 PM

Hi,

I need to assign to an array like char *args[];

for example I have some data as parameters in the *argv[] array.
I need to assign these values starting from argv[1] to argv[argc-1] into the *args[] array.

for (i=1; i<argc; i++)
strcpy(args[i-1], argv[i]);

That doesn't work. Any idea how can I handle this?

Thanks.

tuxdev · 04-09-2007, 06:55 PM

I'm suspecting you need this to call execv. Try

Code:

int i = 0;
char **args = malloc((argc + 1) * sizeof(char *));
while(i < argc) {
   args[i] = argv[i + 1];
   i++;
}
args[argc] = 0;
execv...

If you're adventurous, you can also try

Code:

int i = 0;
while(i < argc) {
   argv[i] = argv[i + 1];
}
execv...

But what you really need to know is that strcpy isn't always appropriate, and direct assignment is okay sometimes.

haydari · 04-09-2007, 07:17 PM

Thank you very much, it worked.

Yes, I will use it with execve :=). I have an assignment about creating a shell terminal executing shell commands with parameters, using execve command.

In your code, could you tell me why do I need to use double pointer, **args? And I hope any error won't appear when I use it like execve(pathname, args, NULL); because of it is a double pointer... (I didn't have enough time to check this in the lab, will try it tomorrow..)

varun_shrivastava · 04-09-2007, 11:48 PM

Code:

 int execve(const char *filename, char *const argv[],
                  char *const envp[]);

2nd argument is nothing but **args

*argv[] is = to **argv