/* * nbtest.c: read and write in non-blocking mode * * This should run with any Unix */#include <stdio.h>#include <unistd.h>#include <fcntl.h>#include <stdlib.h>#include <errno.h>char buffer[4096];int main(int argc, char **argv){    int delay=1, n, m=0;    if (argc>1) delay=atoi(argv[1]);    fcntl(0, F_SETFL, fcntl(0,F_GETFL) | O_NONBLOCK); /* stdin */    fcntl(1, F_SETFL, fcntl(1,F_GETFL) | O_NONBLOCK); /* stdout */    while (1) {        n=read(0, buffer, 4096);        if (n>=0)            m=write(1, buffer, n);        if ((n<0 || m<0) && (errno != EAGAIN))            break;        sleep(delay);    }    perror( n<0 ? "stdin" : "stdout");    exit(1);}