Question

I’m writing a small C application that launchs a Matlab script (.m file).
I need to exchange some variables and I don’t know how to get an array of chars that exists in Matlab.

I’m doing something like this:

enter code here
result = engGetVariable(ep,"X");
if (!result)
    {
    printf ("Error...");
            exit -1;
    }

int n = mxGetN(result);

    char *varx = NULL;
    memcpy(varx, mxGetData(result),n*sizeof(char));

It doesn’t work. Does someone know how to get a Matlab string in C?
I’ve read Matlab documentation about engGetVariable() and the provided example but any of this things clarify me.

Answer 1

Your problem is that you’re trying to memcpy into memory that you never allocated.
char *varx = malloc (sizeof(char) *bytes_you_need); before you do that. Setting char * to NULL means it has no memory address, and thus cannot serve as a reference to any memory…. set it to the return value of malloc, where malloc has set aside some bytes for your data.

char *varx = malloc (sizeof(char) * n);
memcpy(varx, mxGetData(result),n*sizeof(char));
printf ("%s\n", varx);
free(varx);