Thread: Function returning array of strings.

Hi,

I want to write a function to parse a string, which will return the parsed strings in the array format.
I just wanted to know how should I declare my function which will return me an array of strings.
I tried to do something like this:

Code:

char **parse_my_string(char *string_to_be_parsed, char delimiter)
{
     char arr_str[5][10];

      function body;
      return arr_str;
}

That won't work because you're returning a pointer to something that's already been freed. (stack variables are freed when the function exits).

Instead, pass the array of strings to the function and allocate it beforehand.

I have a better idea, (not tested though):
Replace all the 'delimiter's in the 'string_to_be_parsed' with '\0' and return a char** casted 'string_to_be_parsed' .

I tried to allocate char arr_str[5][10] before the function definition. It complied without any errors. But, when I tried to test it in the main, It is giving me error: "error C2664: 'strcpy' : cannot convert parameter 2 from 'char **' to 'const char *' "

How to check it?

I did something like this:

Code:

char test_arr_str[5][10];

int main(void)
{
   -----
  strcpy(test_arr_str, parse_my_string(str, ' '));
  -----
}

What? No.

Modify your function prototype to accept a 2D array (not a global!) and allocate it right before you pass the variable. Also, you need to strcpy() into one of the strings, not the entire array.

I made the following changes:

Code:

char **parse_2D(char parsed_arr[5][20], char *str_to_be_parsed,  char ch)
{
    strcpy(parsed_arr[0], str_to_be_parsed);
    --------
    --------
    return parsed_arr;
}

It is still not working.

How is it not working? What is in str_to_be_parsed? If it's any more than 19 characters long, you have a buffer overflow. Also, you aren't actually parsing str_to_be_parsed. Not just that, you aren't showing us how you declare the 2-d array in main and how you call parse_2D. The error may be in there.

We need a clear description of the problem and all the relevant source code.

something like this:

Code:

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

char **parse_my_string(char [][], char *, char *);

char parsed_str[5][20];
char *str = "abcd efg ij";


int main(void)
{
	int count = 0;

	count = count_spaces(str);

	parse_string(parsed_str , str, ' ');

	for(int i = 0; i <= count; i++)
	{
		printf("%s\n", temp_str[i]);
	}
	
	getchar();

	return 0;

}

char **parse_my_string(char parse_arr[5][20], char *str_to_be_parsed, char *ch)
{
	char *temp;
	char *temp_str;
	int i = 0;

	strcpy(temp_str, str_to_be_parsed);

	temp = strtok(temp_str, ch);

	strcpy(parse_arr[i], temp);
	i++;

	while((temp = strtok('\0', ch)) != '\0')
	{
		strcpy(parse_arr[i], temp);
		i++;
	}
	return parse_arr;
}

Much of what oogabooga mentioned, and what I'm mentioning should result in warnings or errors from your compiler. If you don't see them, turn up the settings, and if you do, fix them!

1. You never allocate space for temp_str, it's just a pointer that points to random/garbage memory. There is nowhere to copy str_to_be_parsed, so most likely, line 35 will cause a seg fault, since you're accessing memory you don't own.
2. In parse_my_string, the ch parameter is a char pointer, but you pass in ' ' (single quotes), which is just a plain char.
3. If your string has two spaces in a row, strtok will skip both of them. That means that count is not an accurate reflection of how many words the string was parsed into (unless your count_spaces function does not do precisely what it's name implies). A better solution would be to make parse_my_string return an int, and have it return i, which is the number of words it found. You no longer need to return the 2-d array since you already declared it and have access to it in main.

I made following changes.

Code:

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


void parse_my_string(char**, char *, char *);
int count_spaces(char*);

int main(void)
{
    int count = 0, i = 0;
    char **parsed_str; 
    char *str = "abcd efg ij";

    count = count_spaces(str);

    parse_my_string(parsed_str , str, ' ');

    for(i = 0; i <= count; i++)
    {
        printf("%s\n", parsed_str[i]);
    }

    getchar();

    return 0;

}

int count_spaces(char* str)
{
	int i, count = 0;
	for(i = 0; i < strlen(str); i++)
	{
		if(str[i] == ' ')
			count++;
	}
	return count;
}

void parse_my_string(char **parse_arr, char *str_to_be_parsed, char *ch)
{
    char *temp;
    char *temp_str;
    int i = 0;

    temp_str = (char *) malloc(strlen(str_to_be_parsed) + 1);

    strcpy(temp_str, str_to_be_parsed);

    temp = strtok(temp_str, ch);

    strcpy(parse_arr[i], temp);
    i++;

    while((temp = strtok(NULL, ch)) != '\0')
    {
        strcpy(parse_arr[i], temp);
        i++;
    }
    parse_arr[i] = NULL;

    free(temp_str);

}