How to check in C if the file is empty?

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How to check in C if the file is empty?

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#1 by (5 votes)
#2 by (0 votes)

7

Good evening,

I'm working with C, and it turns out that I have a function or method that you have to print the data, the meal markings, for students who book a meal on the system.

In the method the system must check if this file is empty and if it is empty it simply prints to the file fprintf(filetmp, "%d %s %s %s \n", num, nome, subnome, meal);

If the file already has, for example, two meals marked by the students, the system must read and print them to filetmp

I have tried to compare the file to see if it is empty, or if you have a meal, I checked and consulted the internet for it and although it exists, I know a ftell(file) function that allows determining how file is empty or no I can not in any way test whether the file has a meal or not.

I also tried feof(file) but it happens that I just run out of the file. How can I change the code for it to check if the file is empty, and to check if the file has any meals.

void PrintMealToFIle(int num, char nome[100], char subnome[250])
    {
        size_t size;
        int i=0, j=0;
        struct Food f;
        struct CantinaAlunoFood aluno;
        const char *filename = "db-cantinameals.txt";
        FILE *file, *filetmp;
        filetmp = fopen("cantinatmp.txt", "w");
        file = fopen(filename, "r");
        size = ftell(file);
        fseek(file, 0, SEEK_END);
        //size = ftell(file);
        while (!(feof(file)))
        {

            if (ftell(file)==0)//se esta vazio
                //fseek(file, 0, SEEK_END);
                //size = ftell(file);

                fprintf(filetmp, "%d %s %s %s \n", num, nome, subnome, meal);

            if (ftell(file)!=0)
            {
                fscanf(file, "%d %s %s %s ", &aluno.id, aluno.name, aluno.subname, aluno.refeicao);
                fprintf(filetmp, "%d %s %s %s \n", num, nome, subnome, meal);
                fclose(filetmp);
                fclose(file);


                if (remove(filename) == 0)
                {
                    printf("\n");
                    printf("Ficheiro removido com sucesso\n");
                }

                else
                    perror("Problema a remover ficheiro ");

                if (rename("cantinatmp.txt", filename) == 0)
                {
                    printf("\n");
                    printf("Ficheiro bem renomeado");
                }

                else
                    perror("Problema ");

            }

        }

    }

c arquivo

asked by anonymous 10.01.2015 / 23:21

2 answers

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score 5 · Answer 1

You can check the size of the file and then check if it is empty.

int get_size(const char* file_name)
{
    FILE *file = fopen(file_name, "r");

    if(file == NULL)
        return 0;

    fseek(file, 0, SEEK_END);
    int size = ftell(file);
    fclose(file);

    return size;
}

Example, verifying that the teste.txt file is empty:

if(get_size("teste.txt") == 0)
{
    printf("O arquivo esta vazio.");
}
else
{
    printf("O arquivo nao esta vazio.");
}

score 0 · Answer 2

You can do a basic replay system to check if there is something in the file

int main(){

   char Arquivo(Array);    //Variáveis
   int i=0;

   FILE *Abrir;   //Abrir e ler o arquivo
   Abrir=fopen(Arquivo,"rt");

      fscanf(Abrir,%c,&Arquivo(i));

      if (Arquivo(i) == Null){ // Condição Se
         printf("Arquivo Vazio");
      } else {printf("Arquivo com dados");}
      break;

   printf("A partir daqui vc resolve o que fazer");

   fclose(Abrir);   //fechando ponteiro
   return 0;
}