How do I pass a file path/ string in main.c?

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Tom Engels
Tom Engels 2022-2-21
评论： Tom Engels 2022-2-22
Hello all,
I have created a shared library with MATLAB Coder. With the programme I want to read data from a path, process it and then output the result again. The input for the MATLAB function is therefore a string (char) of the file path and a few more number arguments (double).
To create the .sh, I have compiled the code accordingly in C and would now like to adapt my main.c. To run it in the Linux terminal, I have to create a new main.c.
In order to be able to execute the .sh in the Linux terminal, I adapt my main function as follows:
int main(int argc, char **argv)
{
char * path =argv[1];
double rpd;
double noc;
rpd = strtol(argv[2],&pEnd_1,10);
noc = strtol(argv[3],&pEnd_2,10);
c_main_test_f(path, rpd, noc);
test_f_terminate();
return 0;
}
In test_f I then pass the values of the function generated by MATLAB Coder. I have defined two return variables for this:
static void c_main_test_f(char path[], double rtg, double az)
{
/* This is autogenerated by MATLAB Coder*/
emxArray_real_T *result_normal;
emxArray_real_T *result_query;
emxInitArray_real_T(&result_query, 2);
emxInitArray_real_T(&result_normal, 2);
printf("Path: %s RTG-value: %f az-value: %f \n", path, rtg, az);
test_f(path, rtg, az, result_query, result_normal);
emxDestroyArray_real_T(result_query);
emxDestroyArray_real_T(result_normal);
}
When I compile this now I get the following error:
/home/user/Desktop/lin_file/test_f.h:26:57: note: expected sconst rtString *e {aka rconst struct > *e} but argument is of type schar *t
In the original function (without input parameters) MATLAB Coder suggests me the following for the string/path:
static emxArray_char_T *argInit_1xUnbounded_char_T(void);
static rtString argInit_rtString(void);
static char argInit_char_T(void);
static char argInit_char_T(void)
{
return '?';
}
static rtString argInit_rtString(void)
{
rtString result;
/* Set the value of each structure field.
Change this value to the value that the application requires. */
result.Value = argInit_1xUnbounded_char_T(pfad_1);
return result;
}
static emxArray_char_T *argInit_1xUnbounded_char_T(void)
{
emxArray_char_T *result;
int idx0;
int idx1;
char *result_data;
/* Set the size of the array.
Change this size to the value that the application requires. */
result = emxCreate_char_T(1, 2);
result_data = result->data;
/* Loop over the array to initialize each element. */
for (idx0 = 0; idx0 < 1; idx0++) {
for (idx1 = 0; idx1 < result->size[1U]; idx1++) {
/* Set the value of the array element.
Change this value to the value that the application requires. */
result_data[idx1] = argInit_char_T();
}
}
return result;
}
And in c_main_test_f:
/* Befor function call*/
rtString path_name;
path_name = argInit_rtString();
/* After function call*/
emxDestroy_rtString(path_name);
Unfortunately, as I am absolutely no C specialist and also new to MATLAB coders, I have no idea how to pass the file path so that my function can use it.
Can anyone help me here?
Many thanks and best regards

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回答（1 个）

Tom Engels
Tom Engels 2022-2-22
编辑：Tom Engels 2022-2-22
Yes, I can help.
You have to disregard the functions predefined by MATLAB Coder.
Using:
Documantation
and:
Similar question
i was able to convert the string/path/group of chars into the struct.
The command in main.c looks like this:
static void c_main_test_f(char *path, double rtg, double az) {
emxArray_char_T *path_str;
/* rows=1, cols = length of the input string */
path_str = emxCreateWrapper_char_T(path, 1, strlen(path));
/* This is autogenerated by MATLAB Coder*/
emxArray_real_T *result_normal;
emxArray_real_T *result_query;
emxInitArray_real_T(&result_query, 2);
emxInitArray_real_T(&result_normal, 2);
printf("Path: %s RTG-value: %f az-value: %f \n", path, rtg, az);
test_f(path_str, rtg, az, result_query, result_normal);
emxDestroyArray_real_T(result_query);
emxDestroyArray_real_T(result_normal);
emxDestroyArray_real_T(path_str);
}
Also you have to include in main.c:
#include <string.h>
#include <stdio.h>
  2 个评论
Tom Engels
Tom Engels 2022-2-22
编辑：Tom Engels 2022-2-22
Now I still have the problem of reading the return values of result_query and result_normal.
My Matlab function returns an array of (n x 3) both times. Where n depends on the size of the read file.
On the one hand, I would like to output this in the terminal and also give this as the return value of the call. (Read the values from emxInitArray_real_T()).
Also, I am not sure if the arrays are initialised correctly. Unfortunately, the documentation is of little help.
-- Docu
void emxInitArray_<name>(emxArray_<name> **pEmxArray, int numDimensions)
Allocates memory for a double pointer to an emxArray.
--
What is meant by "numDimensions"?
Can someone please help me?
Tom Engels
Tom Engels 2022-2-22
numDimensions defines the size of the matrix:
e.g. numDimension = 2 is a struct with (n x n) elements.
One can now simply iterate through this structure, bearing in mind that indexing is done row wise.

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