CODEWITHSUNDEEP
c
sganesh
sganesh

Reputation: 1721

Getting Variable dynamic in c

I have one requirement in C.

char abc[]="hello";
char hello[]="world";

Using abc whether we can get the hello variable's value in C. I know it is possible in some of the languages like Perl, Php, Bash,.,

Is it possible in C?

Upvotes: 3

Views: 209

Answers (6)

qrdl
qrdl

Reputation: 34968

POSIX has several functions that allows you to do it, assuming variable hello is global and isn't static:

void *handle = dlopen(NULL, RTLD_NOW);
// error handling omitted

printf("%s variable contains value %s", abc, (char *)dlsym(handle, abc));

dlsym() return value is casted to char * to suppress warning when using compilers that check format string for printf-alike functions.

And you need to make sure you've specified correct compiler options, e.g. -rdynamic -ldl in case of GCC.

Upvotes: 0

Aaron Digulla
Aaron Digulla

Reputation: 328604

As soon as the C compiler has figured out where to store the underlying pointers, it forgets about the name you gave it. The dynamic languages solve it with a data structure like a hash map which allows you to store the pointers (value) under a key (the name).

Another option is to read in the debug information. This is only available if you compile your code with -g (gcc) or some other, compiler specific option. Note that the debug format is not standardized, so you'll need to figure out what your compiler uses and how to work with it.

Upvotes: 1

Eli Bendersky
Eli Bendersky

Reputation: 273476

It's impossible in C, unlike in more dynamic languages like Perl or Python. However, it's important to keep in mind that even in those languages this isn't recommended. I haven't seen a snippet of code putting this to a good use yet. The eval methods available in dynamic languages are used sparingly, and not for dynamically grabbing variable names.

Upvotes: 1

fastcodejava
fastcodejava

Reputation: 41097

It is not possible in C. It can be done in java by reflection in some cases.

Upvotes: 0

Abubacker Nainamohamed
Abubacker Nainamohamed

Reputation: 4797

Yes you are right , this is possible in some other language but not in C , since abc is a container which resides in a location (for ex: 1000) and hello is one more container which resides in another location ( for ex : 2000 ) , so we have no contact between these two arrays ,

we cannot make a value ( strings ) to point some other value. so finally THIS IS NOT AT ALL POSSIBLE.

Upvotes: 2

Vicky
Vicky

Reputation: 13244

No, this is not possible in C without providing a string lookup table of some sort that could link variables with their names.

Upvotes: 2

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