#include <sys/stat.h>
#include <fcntl.h>

#include <unistd.h>

ssize_t c_write(int fd, const void *buff, int bytesToWrite) {
    size_t bytesWritten;
    for (bytesWritten = 0; bytesWritten < bytesToWrite; ) {
        ssize_t currentlyWritten = write(fd, buff + bytesWritten, bytesToWrite - bytesWritten);
        if (currentlyWritten == 0) {
            return bytesWritten;
        }

        if (currentlyWritten == -1) {
            return -1;
        }

        bytesWritten += currentlyWritten;
    }
    return bytesWritten;
}

ssize_t c_read(int fd, void *buff, int bytesToRead) {
    size_t bytesRead;
    for (bytesRead = 0; bytesRead < bytesToRead; ) {
        ssize_t currentlyRead = read(fd, buff + bytesRead, bytesToRead - bytesRead);
        if (currentlyRead == 0) {
            return bytesRead;
        }

        if (currentlyRead == -1) {
            return -1;
        }

        bytesRead += currentlyRead;
    }
    return bytesRead;
}

int main(int argc, char **argv) {
    int exit_code = 0;

    int in = open(argv[1], O_RDONLY);
    if (in == -1) {
        exit_code = 1;
        goto finally;
    }

    int out_digits = open(argv[2], O_WRONLY | O_CREAT, 0640);
    int out_other = open(argv[3], O_WRONLY | O_CREAT, 0640);
    if (out_digits == -1 || out_other == -1) {
        exit_code = 2;
        goto finally;
    }

    ssize_t in_read, out_d_read, out_o_read;
    char buffer[1024], in_byte;
    int out;

    while ((in_read = c_read(in, &buffer, sizeof(buffer))) > 0) {
        for (int i = 0; i < in_read; ++i) {
            in_byte = buffer[i];
            out = '0' <= in_byte && in_byte <= '9'
                ? out_digits
                : out_other;
            if (write(out, &in_byte, sizeof(in_byte)) == -1) {
                exit_code = 3;
                goto finally;
            }
        }
    }
finally:
    close(in);
    close(out_digits);
    close(out_other);

    return exit_code;
}