Print Linked List in C

Question

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

struct data{ 
    char help[5];
    struct data *next;
    struct data *prev;
}*head = NULL, *tail = NULL, *curr = NULL, *temp = NULL;

void backpush(char input[5]){
    curr = (struct data*) malloc(sizeof(struct data));
    strcpy(curr->help, input);
    if(head == NULL){
        head = tail = curr;
        head->next = NULL;
        head->prev = NULL;
    }
    else{
        tail->next = curr;
        curr->prev = tail;
        curr->next = NULL;
        tail = curr;
    }
}

int main(){
    char code[][5] = {"7R", "4R", "6B", "0B", "8R", "5R", "3B"};
    for(int i = 0;i<7;i++){
        backpush(code[i]);
    }
}

So in int main i try this

curr = head; printf("%s", curr->help[0]);

but the result is error, i add help[0] because i just want to print '7' not '7R', is there something wrong?

curr->help[0] has type char. You can use the %c printf specifier to print it. The %s printf specifier expects a char * pointing to a null-terminated string. — Ian Abbott
– Ian Abbott, Commented Apr 3, 2024 at 15:08
@Fernando Gunawan, Save time and enable all warnings. printf("%s", curr->help[0]); typical generates a warning as to why it is bad. — chux
– chux, Commented Apr 3, 2024 at 15:10
@FernandoGunawan, "the result is error" --> this lacks detail. Better to post the exact error message or description. — chux
– chux, Commented Apr 3, 2024 at 15:12
return value not 0, yeah i just remember the correct is %c not %s — Fernando Gunawan
– Fernando Gunawan, Commented Apr 3, 2024 at 15:19
try printf("first letter of node at head is '%c'\n", curr->help[0]);. If you want to print a single letter use %c specifier. Your code does not even have a list. And do not try to print one, as the topic title suggest. I believe you need a better model... — arfneto
– arfneto, Commented Apr 3, 2024 at 22:55

Eric Postpischil · Accepted Answer · 2024-04-03 15:09:40Z

1

To print a single character, use %c:

printf("%c", curr->help[0]);

To print a string, use %s:

printf("%s", curr->help);

curr->help[0] is a single character.

curr-help is an array, which is converted to a pointer to its first element, so it represents a string by pointing to the first character of a string.

answered Apr 3, 2024 at 15:09

Eric Postpischil

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