How do you pass back an array of char into the main on C?

Question

I'm trying to transfer an array from a function I've created, taking input an array of char and a short, copied below

    char transl [] (char **x, short num){
    char newword []  = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
    short num = num;
    FILE * wd;
    wd  = fopen(argv[1], "r");
    short w=0;
    short arrayle=sizeof(x);
    if (arrayle>9){
    while((c = getchar() != '\n') && c != EOF);
    }
    while(((c = fgetc(wd)) != EOF)&& (num>=1)) {
    if (c == ' ') {
    num--;
    }
    if (num == 1) {
    newword [w] = ((c = fgetc(wd)));
    w++;       
    }
    }
    fclose(wd);
    return newword;
    }

I return the array of set size back into the main in the following way.

     char newDay [32];
     newDay  = transl (engw, daynum);

I get the following error:

assignment to expression with array type

I read on Stack that I would have to pass back a pointer to the array, but wouldnt that pointer be invalid in the main without the array itself being passed back?

Anyways, extremely confused. Please advise, and thank you a lot in advance!

Not clear what you want. See [ask], provide a [mcve]. And format&indent that properly. Your snippet is unreadable. — too honest for this site, Oct 22 '16 at 23:20
Oh, and don't spam tags! This seems not to be C (unless you get an error during compilation). — too honest for this site, Oct 22 '16 at 23:22
I rolled back the "ungolfed" code update. Edits [should not](http://meta.stackoverflow.com/questions/252806/when-should-i-edit-something-vs-comment-on-it-if-its-a-relatively-trivial-error) make substantial changes to posters' code as it could easily change its functionality or make a question invalid. — Robert Columbia, Oct 25 '16 at 04:26

score 1 · Answer 1 · answered Oct 22 '16 at 23:23

In order to pass back an array from a function you need to do one of two things:

Allocate the array in static memory - This approach works only in single-thread systems, and only in situations that do not require re-entrancy
Allocate the array in dynamic memory - This has no restrictions for re-entrancy or concurrency, but the callers will be required to free the memory they receive in order to avoid memory leaks.

Here is an example of the second approach:

char *newword = malloc(30);
memset(newword, 0, 30);
...
return newword;

The caller of your function will need to call

free(resultOfCall);

after he is done processing the returned array.

How do you pass back an array of char into the main on C?

1 Answers1