Assigning string array to char**

Question

I just cannot assign string array to my char** pointer.

I have my strings in char *tempArr[12];

But I don't know how to assign them to my char** arr variable.

First, I allocate memory using: arr = (char**)malloc(numberOfElements * sizeof(char*));

Then I tried to allocate memory to each element:

arr[i] = malloc(256 * sizeof(char));

I also tried to alocate just the memory for char pointer but neither works. The result in my arr variable is 2 to 3 nonsense characters.

What could be wrong? I tried everything I was able to find and the result is either crash or nonsense content.

EDIT: Sorry I'll try to clarify it more. Background is, I am loading data from file into structs. Each struct has char** variable that is suppose to hold strings array.

In my reading code, I am using my temp array char* tempArr[12] and successfully loading strings into it. Then I pass it allong to my function that is creating my structs.

The problem starts here, I was trying to "convert" my passed array so it can be stored in char** arr variable.

There are too many things missing in this question to provide an accurate answer with wagging (wild-ass-guessing). Your arr = ... makes sense (more-so if you lose the cast, which for some odd reason you did incorrectly there, but correctly in your arr[i] = ... assignment). If this is entirely self-contained in some function scope, it looks right. If char **arr is a function out-parameter, then its wrong. Post an MCVE of the REAL problem. — WhozCraig
– WhozCraig, Commented Jan 2, 2015 at 15:14

Gopi · Accepted Answer · 2015-01-02 15:08:26Z

2

char *tempArr[12];

Is array of pointers. So if you have something like

tempArr[0] = malloc(20);
strcpy(tempArr[0],"hello");

Then after what you are doing you can do. i.e. After allocating memory to your the pointer arr[i]

char **arr = malloc(numberOfElements * sizeof(char*));

arr[i] = malloc(256);

strcpy(arr[i],tempArr[0]);

You can run the above steps in a loop to copy values for all your pointers

edited Jan 2, 2015 at 15:08

answered Jan 2, 2015 at 15:03

Gopi

19.9k4 gold badges28 silver badges37 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Filip Over a year ago

Yeah, that's it. Thanks. My problem was in the for cycle (I counted number of elements and didn't factor in that array starts at zero) so while I was trying this before I thought it doesn't work when in fact problem was elsewhere :/

Vlad from Moscow · Accepted Answer · 2015-01-02 15:12:08Z

2

I think that you mean the following

#include <string.h>

//...

size_t i;

char **arr = ( char** )malloc( numberOfElements * sizeof( char* ) );
for ( i = 0; i < numberOfElements; i++ ) arr[i] = malloc( 256 * sizeof( char ) );

for ( i = 0; i < sizeof( tempArr ) / sizeof( *tempArr ); i++ ) strcpy( arr[i], tempArr[i] );

edited Jan 2, 2015 at 15:12

answered Jan 2, 2015 at 15:06

Vlad from Moscow

313k27 gold badges204 silver badges358 bronze badges

Collectives™ on Stack Overflow

Assigning string array to char**

2 Answers 2

1 Comment

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Related