在 C 中逐字读取文本文件

Question

I am trying to learn file I/O operations in C. My aim is storing all the words to a string array from a text file.

I tried to write a code that reads text file char by char and creates words from those chars. What I want to do is accessing to a word with line and word index. Would you help me about this?

This is my code.

char words[MAX_LINE][MAX_WORDS][MAX_CHAR];
int i=1, j=1, k=1;

FILE* ptrbook;
if((ptrbook = fopen("trial.txt", "r")) == NULL)
{
    printf("Failed to open the file %s\n", filename);
}
else
{
    while((words[i][j][k] = getc(ptrbook)) != EOF)
    {
        while((words[i][j][k] = getc(ptrbook)) != '\n')
        {
            while((words[i][j][k] = getc(ptrbook)) != ' ')
            {
                words[i][j][k] = getc(ptrbook);
                k++;
            }
            if((words[i][j][k] = getc(ptrbook)) == ' ' )
            {
                j++;
                k=1;
            }
            if((words[i][j][k] = getc(ptrbook)) == '\n')
            {
                i++;
                j=1;
                k=1;
            }
        }
    }
}
printf("%s\n", words[1][1]);

Answer 1

For doing this issue is easiest reading all the content from file into a dynamic variable in the heap. So after define a variable use the below function to allocate the dimension for the variable.

#define SIZE 4096
char * malloc_buff(int dim){
    char *buf;
    buf=malloc(sizeof(char)*dim);
    if(buf==NULL){
        perror("Errore in malloc");
    }
    return buf;
}

Then you perform a variable and store all the information of the file in that variable using the below function. Instead of database_prenotazioni.txt insert the name of your file name

char * lettura_database_prenotazioni(){
    FILE* fd;
    char* disponibili;
    disponibili=malloc_buff(SIZE);
    errno=0;
    fd=fopen("database_prenotazioni.txt","r+");
    if(errno!=0){
        fprintf(stderr,"error in open\n");
        exit(-1);
    }
    fread(disponibili,sizeof(char),SIZE,fd);
    if(fclose(fd)){
        fprintf(stderr,"error in closure\n");
        exit(-1);
    }
    return disponibili;
}

Now you need to make a strtok of the variable in which you have all the content with the del \t. Remember to allocate a new variable as array_stringhe variable in the below function that should be used for the return of the function

char ** tokenize_elem(char *buffer,char *del){
    int c=1;
    char **array_stringhe=malloc((sizeof(char*)*SIZE));
    if(array_stringhe==NULL){
        fprintf(stderr,"errore in malloc\n");
        exit(EXIT_FAILURE);
    }

    char *token=malloc_buff(SIZE);
    memset(token,'\0',SIZE);
    memset(array_stringhe,'\0',SIZE);
    array_stringhe[0] = strtok (buffer,del);
    //fprintf(stdout,"%s\n",array_stringhe[0]);
    while(token!=NULL){
        token=strtok(NULL,del);
        if(token==NULL){
            break;
        }
        array_stringhe[c]=token;

        //fprintf(stdout,"%s\n",array_stringhe[c]);
        c++;

    }
    free(token);
    return array_stringhe;
}

Answer 2

Try to call getc(ptrbook) only once per loop and store the result temporarly. Than you can check for the splitting characters such as white space and line breaks. Currently you are jumping in each while loop from character to character, which is not what you want here.

Do something like this:

int c;
while((c = getc(ptrbook)) != EOF){
    if(c == ' ') 
        j++;
    else if(c == '\n') 
        i++;
    else 
        words[i][j][k++] = c;
}