/*
 * Copyright (c) 2020, Dive into Systems, LLC (https://diveintosystems.org/)
 *
 * Extract whitespace-delimited tokens from a line of input
 * and print them one per line.
 *
 * to compile:
 *   gcc -g -Wall strtokexample.c
 *
 * example run:
 *   Enter a line of text:        aaaaa             bbbbbbbbb          cccccc
 *
 *   The input line is:
 *         aaaaa             bbbbbbbbb          cccccc
 *   Next token is aaaaa
 *   Next token is bbbbbbbbb
 *   Next token is cccccc
 */

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

int main(void) {
     /* whitespace stores the delim string passed to strtok.  The delim
      * string  is initialized to the set of characters that delimit tokens
      * We initialize the delim string to the following set of chars:
      *   ' ': space  '\t': tab  '\f': form feed  '\r': carriage return
      *   '\v': vertical tab  '\n': new line
      * (run "man ascii" to list all ASCII characters)
      *
      * This line shows one way to statically initialize a string variable
      * (using this method the string contents are constant, meaning that they
      *  cannot be modified, which is fine for the way we are using the
      *  whitespace string in this program).
      */
    char *whitespace = " \t\f\r\v\n";  /* Note the space char at beginning */

    char *token;  /* The next token in the line. */
    char *line;   /* The line of text read in that we will tokenize. */

    /* Allocate some space for the user's string on the heap. */
    line = malloc(200 * sizeof(char));
    if (line == NULL) {
        printf("Error: malloc failed\n");
        exit(1);
    }

    /* Read in a line entered by the user from "standard in". */
    printf("Enter a line of text:\n");
    line = fgets(line, 200 * sizeof(char), stdin);
    if (line == NULL) {
        printf("Error: reading input failed, exiting...\n");
        exit(1);
    }
    printf("The input line is:\n%s\n", line);

    /* Divide the string into tokens. */
    token = strtok(line, whitespace);       /* get the first token */
    while (token != NULL) {
        printf("Next token is %s\n", token);
        token = strtok(NULL, whitespace);     /* get the next token */
    }

    free(line);

    return 0;
}