How to use the "fread" function in c to read a txt file string and store that string in an array?

Question

Hello, I’m trying to read a block of bytes from a file. txt that contains a string for example, I want to store that string in a char array.

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


    char nome_arquivo[25];
    int i, j;
    char vetor[50]; //vetor que receberá a mensagem do arquivo nessa função
    //vetor = malloc(50*sizeof(char));
    int tamanhovetor;
    char cpy[2];
    char str[5][9];

    printf("Informe o nome do arquivo que deseja abrir:\n");
    scanf("%s", nome_arquivo);

    arquivo_txt = fopen(nome_arquivo, "r");

    if(arquivo_txt == NULL){
        fprintf(stderr, "Erro na abertura do arquivo\n");
        fclose(arquivo_txt);
    }

    fread(vetor, sizeof(char), 5, arquivo_txt);

    tamanhovetor = strlen(vetor);

    printf("%s\n%d", vetor, tamanhovetor);  

    /*
    for(i=0; i<tamanhovetor; i++){
        str[i][0]= '\0';
        for(j=0; j<9; j++){
            sprintf(cpy,"%d", vetor[i]%2);
            strcat(str[i], cpy);
            vetor[i]/=2;
        }
            printf("%s ", str[i]);
    }*/
}

Answer 1

You are copying 5 bytes of your file to a buffer (vetor) and then calling strlen() in it, which is a function that counts at which position of the vector it receives is the first byte '\0'.

But you didn’t put one '\0' after the end of bytes that you copied, and how the vetor is a local variable, it is allocated to the stack, which does not have its values zeroed.

So unless you guarantee that one of the 5 (why 5?) bytes read is null, you are most likely starting to read the bytes that you carried and going on reading the trash in the rest of the vetor and then going on reading random values on the stack, until it reaches the end of the stack and takes an access violation...

So you have to put after the call to fread() the following line:

vetor[5] = '\0';

Thus the string is delimited and manipulation functions make sense.

Answer 2

this code can help

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

int main()
{
   FILE *fp;
   char c[] = "this is tutorialspoint";
   char buffer[100];

   /* Open file for both reading and writing */
   fp = fopen("file.txt", "w+");

   /* Write data to the file */
   fwrite(c, strlen(c) + 1, 1, fp);

   /* Seek to the beginning of the file */
   fseek(fp, SEEK_SET, 0);

   /* Read and display data */
   fread(buffer, strlen(c)+1, 1, fp);
   printf("%s\n", buffer);
   fclose(fp);

   return(0);
}

Answer 3

int c =50; int t=80; c+t=h; printf("%i",h);