Strtok does not return more tokens even though there are more to be read

Question

I am havin this issue where if I input a string of words separated by commas with no leading nor trailing spaces, I got my expected outputs. But, when I add spaces I just get one of the outputs without the spaces even though I don't have code that does that. It seems likes strtok only reads the first one when there are spaces, even though there are more.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#define SIZE 40

void main() {
    char input[SIZE];
    
    printf("Enter list of words separated by commas: ");
    scanf("%30s", input);

    char *arr = strtok(input, ",");
    word *head, *current, *next;
    current = (word*) malloc(sizeof(word));
    assert(current != NULL);
    head = current;
    
    while (arr != NULL) {
        next = (word*) malloc(sizeof(word));
        assert(next != NULL);    
        // deleteWhiteSpaces(arr);
        strcpy(current->value, arr);
        arr = strtok(NULL, ",");
        if (arr != NULL) {
            current->next = next;
            current = next;
        }
    }

    current = head;
    while (current) {
        printf("'%s' %p\n", current->value, current);
        current = current->next;
    }
    
}

Fundamentally, the problem here is you did not verify the data you were processing was properly and completely read. — Andrew Henle, Oct 25 '22 at 16:03

Andreas Wenzel · Answer 1 · 2022-10-25T16:02:38.803

The line

scanf("%30s", input);

which you are using will only read a single word of input.

The line

fgets( input, sizeof input, stdin );

will read an entire line of input, including the '\n' character.

Therefore, I suggest that you use fgets instead, but remove the trailing newline character, as described here:

Removing trailing newline character from fgets() input

The easiest way to do this is probably like this:

//attempt to read one line of input
if ( fgets( input, sizeof input, stdin ) == NULL )
{
    fprintf( stderr, "input error!\n" );
    exit( EXIT_FAILURE );
}

//remove newline character, if it exists
input[strcspn(input,"\n")] = '\0';

Here, the newline can be taken care of with the `strtok` character set, say `", \t\n"`. — Weather Vane, Oct 25 '22 at 16:46

Strtok does not return more tokens even though there are more to be read

1 Answers1