在C中逐行读取每个char

Question

I was looking for a solution on how to read char by char on each line from a txt file and I found one, but I don't get some parts of the code. This is it:

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

void handle_line(char *line) {
  printf("%s", line);
}

int main(int argc, char *argv[]) {
    int size = 1024, pos;
    int c;
    char *buffer = (char *)malloc(size);

    FILE *f = fopen("myfile.txt", "r");
    if(f) {
      do { // read all lines in file
        pos = 0;
        do{ // read one line
          c = fgetc(f);
          if(c != EOF) buffer[pos++] = (char)c;
          if(pos >= size - 1) { // increase buffer length - leave room for 0
            size *=2;
            buffer = (char*)realloc(buffer, size);
          }
        }while(c != EOF && c != '\n');
        buffer[pos] = 0;
        // line is now in buffer
        handle_line(buffer);
      } while(c != EOF); 
      fclose(f);           
    }
    free(buffer);
    return 0;
}

It was written by someone from here, but I can't reply 'cause I need more points lol. The parts I don't understand are:

if(c != EOF) buffer[pos++] = (char)c;

What does buffer[pos++] do? does it actually increase the variable "pos"? also, why does it start at 1 instead of 0? (pos starts at 0). I can't really get track of the variable "pos", and I don't know why here buffer[pos] is 0:

buffer[pos] = 0;

The way I read the code is: declare the size of the buffer that contains every char of every line (I mean, buffer is just free'd at the end, so it keeps the information on every line right?), then declare the other variables and alloc the memory of the buffer. Open the file myfile.txt, and if it's not null, make pos = 0, then make "c" to store the first character of the file (now the function points to the next char), then if c != EOF meaning the end of file is not reached, save the character "c" in the position 1 of the buffer (I get confused here, why 1 and not 0). Then realloc twice as memory as before if needed. Do that for every character in the line untile you reach EOF or a \\n. Now make buffer[pos] = 0, I dont know what value "pos" has, and I assume he makes buffer[pos] = 0 to indicate the end of the line? idk. Print the line, do that until you reach the end of the file. Close the file, free the memory on buffer.

Help! thanks.

Answer 1

fgetc(fp) - Reads the next character from the specified input stream (fp) and advances the associated file position indicator (you do not need to). If successful, the function will return the character read; otherwise, the value EOF (-1) is returned.

Here is a very simple example of using fgetc() to read each character of a file (and write it to another file using fputc())

char filename1[]={"c:\\play\\_in.txt"};//change paths as needed
char filename2[]={"c:\\play\\_out.txt"};

int main(void)
{
    FILE *fp1 = {0};
    FILE *fp2 = {0};
    int c=0;

    fp1 = fopen(filename1, "r");
    if(fp1)
    {
        fp2 = fopen (filename2, "w");
        if(fp2)
        {
            c = fgetc(fp1);
            while(c != EOF)
            {
                fputc(c, fp2);
                c = fgetc(fp1);
            }
            fclose(fp2);            
        }
        fclose(fp1);
    }

    return 0;
}