Efficent way of breaking a string into an array based on a character eg.% in C?

Question

Could find a similar thing for C here.

I need to break a sentence into a an char array based on occurrence of a character example: %

Example

If my sentance is my%healthy%dog then i should be able to get my, healthy and dog separately. This could be in a loop as well.

tx

Answer 1

Check out the function strtok in string.h.

This is a good tutorial of how it works: http://www.cplusplus.com/reference/clibrary/cstring/strtok/

Answer 2

The solution is strtok() in string.h.

Here's a good example of how to use.

/* strtok example by [email protected]
 *
 * This is an example on string tokenizing
 *
 * 02/19/2002
 *
 * http://www.metalshell.com
 *
 */

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

int main(int argc, char *argv[])
{
        int x = 1;
        char str[]="this:is:a:test:of:string:tokenizing";
        char *str1;

        /* print what we have so far */
        printf("String: %s\n", str);

        /* extract first string from string sequence */
        str1 = strtok(str, ":");

        /* print first string after tokenized */
        printf("%i: %s\n", x, str1);

        /* loop until finishied */
        while (1)
        {
                /* extract string from string sequence */
                str1 = strtok(NULL, ":");

                /* check if there is nothing else to extract */
                if (str1 == NULL)
                {
                        printf("Tokenizing complete\n");
                        exit(0);
                }

                /* print string after tokenized */
                printf("%i: %s\n", x, str1);
                x++;
        }

        return 0;

}

The thing that confuses people about strtok is the first time you call the method the first argument you pass in a pointer to the string you want to tokenize and on subsequent calls you pass NULL. strtok uses a static variable in it's implementation to keep track of where it should start start searching from in subsequent calls.

• Passing NULL you're telling strtok to continue searching from where we left off last time.
• Passing in a pointer != NULL you're telling the tokenizer that you are starting at the beginning of a new string so disregard previous state information.

Answer 3

strtok is the standard C function to achieve string tokenizing.

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

int main()
{
        char c[] = "my%healthy%dog";
        char *token = strtok(c, "%");
        while (token != NULL)
        {
                printf("%s\n", token);
                token = strtok(NULL, "%");
        }
        return 0;
}


$ ./a.exe
my
healthy
dog

Also note that strtok uses static variables internally, so it is not threadsafe. For threadsafety, you'll have to use the strtok_r function.

Answer 4

using strtok.

Refer this:

Answer 5

strtok() should do the trick. You can also call it repetitively with NULL as the first argument to search from where you left off.

From documentation:
Each subsequent call, with a null pointer as the value of the first argument, starts searching from the saved pointer and behaves as described above.