How to save a splitted string in character array contained in structure in C?

Question

As said in the title, I would like to save each part of my text in character array contained in my structure called Identity, here is the code:

#include <stdio.h>
#include <string.h>

char strExample[]="Andrew;Smith;18;Wall Street;New York;10011;USA";

typedef struct  Identity{
    char firstName[20];
    char lastName[20];
    char age[5];
    char street[64];
    char city[20];
    char postCode[8];
    char country[20];
}Identity;

void textParse()
{
  char *ptr = strExample; 
  char *token;
  int i = 0;
  while ((token= strsep(&ptr,";")) != NULL)
  {
    printf("%s\n",token);
  }
}

int main(int argc, char **argv) {

    textParse();

    return 0;
}

The splitting works well but I don't find how to save every single token in Identity struct. How can I do it?

Please change the wording: You are not saving strings in a typedef; you are saving them in a chanacter array contained in a structure. The typedef is just there to name the child. Also you cannot store anything in a type; you can store things in variables. — U. Windl
– U. Windl, Commented Jan 13, 2021 at 10:40
Do a length check to verify each token fits in the each target char array and then memcpy it there. — Petr Skocik
– Petr Skocik, Commented Jan 13, 2021 at 10:43
Yes, I was thinking of doing something like that, but how do you do it with a loop? — Blovnar
– Blovnar, Commented Jan 13, 2021 at 10:48

Roberto Caboni · Accepted Answer · 2021-01-13 11:12:43Z

Just define a variable of type Identity, and then use strncpy() to copy each token into the relevant field of the struct:

#include <stdio.h>
#include <string.h>

#define STRNCPY_STRUCT_EL(string_field, src) strncpy(string_field, src, sizeof(string_field) - 1 )

char strExample[]="Andrew;Smith;18;Wall Street;New York;10011;USA";

typedef struct  Identity{
    char firstName[20];
    char lastName[20];
    char age[5];
    char street[64];
    char city[20];
    char postCode[8];
    char country[20];
}Identity;

void textParse(Identity *id)
{
  char *ptr = strExample; 
  char *token;
  int i = 0;

  memset(id, 0, sizeof(*id));
  while ((token = strsep(&ptr,";")) != NULL)
  //while ((token = strtok(ptr,";")) != NULL) //I used this in my test
  {
    // ptr = NULL; //I used this in my test, to fit strtok
    switch(i++)
    {
        case 0:
            STRNCPY_STRUCT_EL(id->firstName, token);
            break;
        case 1:
            STRNCPY_STRUCT_EL(id->lastName, token);
            break;
        case 2:
            STRNCPY_STRUCT_EL(id->age, token);
            break;
        case 3:
            STRNCPY_STRUCT_EL(id->street, token);
            break;
        case 4:
            STRNCPY_STRUCT_EL(id->city, token);
            break;
        case 5:
            STRNCPY_STRUCT_EL(id->postCode, token);
            break;
        case 6:
            STRNCPY_STRUCT_EL(id->country, token);
            break;
    }    
  }
}

int main(int argc, char **argv) {
    Identity id;

    textParse(&id);

    printf("Identity:\n%s %s, %s y.o.\nLives in %s, %s (%s - %s)\n",
           id.firstName, id.lastName, id.age, id.street, id.city, id.postCode, id.country);

    return 0;
}

Basically I checked the position of the token and then I copied it in the corresponding position of the struct. I used a switch-case. Not so elegant but it works
I copied it using a macro that automatically calculates the size of the field. I want to copy size-1 characters as I want to leave room for the string terminator '\0'
It works because I previously memseted the whole struct to 0, so that after strncpy the string terminator is for sure where it must be
I had to change textParse() signature in order to accept a pointer to Identity. Inside it I skipped sanity checks (for example checks against NULL pointers). I recommend adding them into your final implementation
This implementation truncates any token longer than the corresponding Identity field

Output:

Identity:
Andrew Smith, 18 y.o.
Lives in Wall Street, New York (10011 - USA)

Petr Skocik · Accepted Answer · 2021-01-13 11:06:12Z

If you want to process it in a loop, you need to have info on the member arrays--their size and offset--accumulated in an array (arrays are most convenient) beforehand:

Example:

#include <stdio.h>
#include <string.h>
#include <stddef.h>

char strExample[]="Andrew;Smith;18;Wall Street;New York;10011;USA";

typedef struct  Identity{
    char firstName[20];
    char lastName[20];
    char age[5];
    char street[64];
    char city[20];
    char postCode[8];
    char country[20];
}Identity;

void textParse(Identity *Id)
{
  static size_t const sizes[7]={
      sizeof((Identity){0}.firstName),
      sizeof((Identity){0}.lastName),
      sizeof((Identity){0}.age),
      sizeof((Identity){0}.street),
      sizeof((Identity){0}.city),
      sizeof((Identity){0}.postCode),
      sizeof((Identity){0}.country),
  };
  static size_t const array_offsets[7]={
      offsetof(Identity,firstName),
      offsetof(Identity,lastName),
      offsetof(Identity,age),
      offsetof(Identity,street),
      offsetof(Identity,city),
      offsetof(Identity,postCode),
      offsetof(Identity,country),
  };

  char *ptr = strExample;
  char *token;
  for (int i=0; (token= strsep(&ptr,";")) != NULL; i++)
  {
      size_t const size = (size_t)(ptr-token);
      if(size > sizes[i]) return; /*doesn't fit*/
      else memcpy((char*)Id+array_offsets[i], token, size);
  }
}

int main(int argc, char **argv) {

    Identity id; textParse(&id);
    puts("=============");
    puts(id.firstName);
    puts(id.lastName);
    puts(id.age);
    puts(id.street);
    puts(id.city);
    puts(id.postCode);
    puts(id.country);

    return 0;
}

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