I had some issues with the strtok function. Here’s a detailed explanation and usage for it.

The strtok function is used to tokenize a string and thus separates it into multiple strings divided by a delimiter.

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

int main() {
    int j, i = 0;
    char delim[4];
    char user_input[81], *token[80];
    user_input[0] = 0;  // set first byte to 0 to detect empty string

    // validate the string length
    while (strlen(user_input) <= 1 || strlen(user_input) > 82) {
        printf("Feed me a string to tokenize: ");
        fgets(user_input, sizeof(user_input), stdin);

    printf("And a delimiter (up to 4 chars): ");
    fgets(delim, sizeof(delim), stdin);

    token[0] = strtok(user_input, delim);  // first call returns pointer
                                           // to first part of user_input
                                           // separated by delim
    while (token[i] != NULL) {
        token[i] = strtok(NULL, delim);  // every call with NULL uses
                                         // saved user_input value and
                                         // returns next substring

    for (j=0; j<=i-1; j++) {
        printf("%sn", token[j]);

    return 0;

Let’s compile and execute it:

Feed me a string to tokenize: foo/bar/baz
And a delimiter: /

The first call to strtok returns the pointer to the first substring. All the next calls with the first argument being NULL use the string passed at the first call and return the next substring. The function returns NULL if no more substrings are available.