C language - printing some sentences to file

Question

I want to read strings and write them as full lines into a file, but I can't read more words into a buffer as a complete string.

Current problematic code:

printf("\nEnter how many sentences do you want to read: ");
    scanf("%d", &n);
    tab = (char**)malloc(n * sizeof(char*));
        for (int i = 0; i < n; i++) {
            printf("\nEnter sentence: ");
            scanf("%s", val);
            tab[i] = _strdup(val);
        }
        for (i = 0; i < n; i++)
            fprintf(f, "%s ", tab[i]);
        free(tab);

Previously I tried this: (problem is this only assigns one string)

printf("\nEnter how many sentences do you want to read: ");
    scanf("%d", &n);
    for (i = 0; i < n; i++) {
        printf("\nEnter sentence: ");
        scanf("%s", val);
        fprintf(f, "\%s ", val);
    }

Almost there, now i have sentences but i got one empty line as first line of file.

#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <conio.h>
#include <stdlib.h>
#include <malloc.h>
#include <string>
#define SIZE 30

void creare(char t[30]);

void main(void)
{
    FILE* f2;
    char name[30];
    printf("\nEnter name of file to work with: ");
    scanf("%s", name);
    creare(name);
    f2 = fopen(name, "r");
    if (f2 == NULL)
    {
        printf("\nOpen error!!");
        exit(0);
    }
    fclose(f2);
    printf("\n");
    _getch();
}


void creare(char t[30])
{
    FILE* f;
    int n,i;
    char val[30];
    f = fopen(t, "w");
    if (f == NULL)
    {
        printf("\nOpen error!!");
        exit(0);
    }
    printf("\nEnter how many sentences do you want to read: ");
    scanf("%d", &n);
    for (i = 0; i <= n; i++)
    {
        fgets(val, sizeof(val), stdin);
        fprintf(f, "% s", val);
    }
    fclose(f);
}

Welcome to Stack Overflow! [Please see this discussion on why not to cast the return value of `malloc()` and family in `C`.](http://stackoverflow.com/q/605845/2173917). — Sourav Ghosh, Jan 13 '17 at 18:54
Note: you free `tab` before freeing each `tab[i]`. You need to `free` the value returned from `strdup`. — 001, Jan 13 '17 at 18:59
"I can't read more words in one string." --> do not use `scanf("%s", val);` Use `fgets(val, sizeof val, stdin)` — chux - Reinstate Monica, Jan 13 '17 at 19:05
@chux almost there. i get one empty line first and n sentences after. why empty space? :( — AndreiD, Jan 13 '17 at 19:09
Your problem is because your mixing `scanf("%s", val);` (which left the in `stdin`) with `fgets()`. Suggest only using `fgets()` for input. Many dupes on this in SO. — chux - Reinstate Monica, Jan 13 '17 at 19:34
You didn't fix his broken `free(tab)` statement as mentioned in one of the comments above — clearlight, Jan 13 '17 at 19:08
@clearlight I'm new and i'm sorry. i will follow rules from now. It's not free(tab) fault. problem is on val assign as pointer there. — AndreiD, Jan 13 '17 at 19:12

score 2 · Accepted Answer · answered Apr 09 '17 at 05:39

I have used fgets(val, sizeof val, stdin) to read the string, because to read string with spaces. The reason why that blank line comes in file is due to the fact that you are reading "\n" that is inputted after scanf("%d", &n);The keystroke "\n" will be read into val for the first time so it simply prints that "\n" to the file.

In order to read that "\n" use a character to read that "\n". Below is the complete program.

#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <stdlib.h>
#include <malloc.h>
#include <string.h>
#define SIZE 30

void creare(char t[30]);

int main(void)
{
    FILE* f2;
    char name[30];
    printf("\nEnter name of file to work with: ");
    scanf("%s", name);
    creare(name);
    f2 = fopen(name, "r");
    if (f2 == NULL)
    {
        printf("\nOpen error!!");
        exit(0);
    }
    fclose(f2);
    printf("\n");
}


void creare(char t[30])
{
    FILE* f;
    int n,i;
    char val[30],g;
    f = fopen(t, "w");
    if (f == NULL)
    {
        printf("\nOpen error!!");
        exit(0);
    }
    printf("\nEnter how many sentences do you want to read: ");
    scanf("%d", &n);
    scanf("%c",&g);
    for (i = 0; i <n; i++)
    {
        fgets(val, sizeof(val), stdin);
        fprintf(f, "%s", val);
    }
    fclose(f);
}

C language - printing some sentences to file

1 Answers1