low-io.c

#include<stdio.h>

main() {
    char buf[BUFSIZ];
    int ch;

    /* getchar using a single element buffer */
    int getchar(void) {
        char c;
        return (read(0,&c,1)==1) ? (unsigned char) c : EOF;
    }

    while((ch=getchar())!=EOF) {
        printf("%c",ch);
    }
}