How to hand over values to a double-pointer and print the values out as if it would be an multidimensional array? (C)

Question

I have following struct defined which I can not change:

typedef struct _content {
    int length;
    char **lines;    
} content_t;

I initialized it in the main function like that:

struct _content cont;
cont.length = 6;
cont.lines[cont.length-1][255];

I try to assign a value to a certain element of the multidimensional array and also to print the value out- which doesn't work:

cont.lines[1][1] = "A";
printf("\n\n%c", cont.lines[1][1]);

What am I doing wrong here? Many Thanks

`lines` is not initialized, so you can't dereference it. – Osiris Jan 25 '19 at 22:26 — Osiris, Jan 25 '19 at 22:26
allocate memory for your char **lines first – Spinkoo Jan 25 '19 at 22:29 — Spinkoo, Jan 25 '19 at 22:29

score 3 · Accepted Answer · answered Jan 25 '19 at 22:36

3

int main(){

content_t cont;
cont.length = 6;
cont.lines=malloc(sizeof(char*)*cont.length);

for(int i=0;i<cont.length;i++) cont.lines[i]=malloc(255);

printf("\n\n%c", cont.lines[1][1]);


for(int i=0;i<cont.length;i++) free(cont.lines[i]);
free(cont.lines);


}

that's the right way to do it

answered Jan 25 '19 at 22:36

Spinkoo

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Thanks a lot for your help. One more question: How can I assign a value to cont.lines[1][1] ? – D.J.A. Jan 25 '19 at 22:43
1

just like that: inhalt.lines[1][1] = 'D'; – D.J.A. Jan 25 '19 at 22:48
1

You could also do something like this after the memory for each line is allocated: `strcpy(cont.lines[i], "hello");` – bruceg Jan 25 '19 at 23:20

How to hand over values to a double-pointer and print the values out as if it would be an multidimensional array? (C)

1 Answers1