my_more.c

// Group members:
//
// - Iñigo Arnedo
// - Elena Hernandez
// - Aritz Lopez
// - Ane Odriozola

#include <stdio.h>
#include <unistd.h>
#include <termios.h>

#define TRUE 1
#define FALSE 0

int one_page(FILE* fd, int max) // Writes one page
{
    int c;
    int n = 0;
    while (n < max && (c = getc(fd)) != EOF) {
        putc(c, stdout);
        if (c == '\n') n++;
    }
    return n;
}

int one_line(FILE* fd) // Writes one line
{
    int c = 0; // Can be anything except '\n'
    // write chars while its not EOF and last char was not newline
    while (c != '\n' && (c = getc(fd)) != EOF) putc(c, stdout);
    return c == '\n'; // returns 1 if last char was '\n' => one line was written
}

void setRaw(int echo)
{
    struct termios t;

    tcgetattr(STDIN_FILENO, &t); //get the current terminal I/O structure

    if (echo) t.c_lflag &= ~(ICANON | ECHO);
    else      t.c_lflag |=   ICANON | ECHO;

    tcsetattr(STDIN_FILENO, TCSANOW, &t); //Apply the new settings
}

int main(int argc, char *argv[]) {
    if (argc != 2 && argc != 3)
    {
        fprintf(stderr, "Usage: %s filename [page_size]\n", argv[0]);
        return 1;
    }
    int pageSize = 24;
    if (argc == 3) pageSize = atoi(argv[2]);
    if (pageSize < 1) {
        fprintf(stderr, "error: page_size must be a positive number!");
        return 2;
    }

    FILE* f = fopen(argv[1], "r");
    if (f == NULL)
    {
        perror(argv[1]);
        return 3;
    }

    setRaw(TRUE);
    int l = one_page(f, pageSize) == pageSize;
    while (l)
    {
        char c;
        // getc returns EOF when end of file has reached or an error occurred
        if ((c = getc(stdin)) == EOF)
        {
            // If an error has occured
            if (ferror(f))
            {
                perror(argv[1]);
                fclose(f);
                setRaw(FALSE);
                return 4;
            }
            break;
        }

        // The next line is to check if the Down Arrow has been
        // pressed (not asked, so not implemented, but tested :P)
        //
        // c == 27 && getc(stdin) == 91 && getc(stdin) == 'B'

        if (c == '\n') // Enter = one line more
        {
            l = one_line(f) == 1;
        }
        else if (c == ' ') // Space = one page more
        {
            l = one_page(f, pageSize) == pageSize;
        }
        else if (c == 'q') break; // q = quit
    }
    fclose(f);
    setRaw(FALSE);
    return 0;
}