Extra \1 Character In Printf

Question

I'm working on a C program to solve the Dining Philosophers' problem. I loop through 500 philosopher state changes, and output each philosophers' status on each interation with the following statement:

printf("  %d> |%s|%s|%s|%s|%s 
", i, get_state(phils[0]), get_state(phils[1]), get_state(phils[2]), get_state(phils[3]), get_state(phils[4]));

For context, here is the function get_state, which converts a numeric philosopher status into a string:

char * get_state(int t) {
    if (t == 1)
        return "  Thinking   ";
    if (t == 2)
        return "   Hungry    ";
    if (t == 3)
        return "   Eating    ";
    return "----Error----";
}

My problem is this: every 5-30 lines, one of them will start with the unicode character U+0001. It appears that it is probably being inserted after the of the previous line, but I can't tell what causes it at all!

I've provided a screenshot for clarity:

And here is the whole loop:

for (i = 1; i <= MAX; i++) {
    silent = 0;
    // receive message from child node
    for (j = 0; j < PHIL_NO; j++) {
        if(phils[j] == EATING) {
            count[j]++;
        }
        lastPhils[j] = phils[j];
    };
    read(host[READ], &msg, sizeof(msg));
    phils[msg.index] = msg.state;


    for (j = 0; j < PHIL_NO; j++) {
        if (phils[j] == lastPhils[j]) 
        {
            silent++;
        }
    };

    printf("%4d> |%s|%s|%s|%s|%s 
", i, get_state(phils[0]), get_state(phils[1]),
            get_state(phils[2]), get_state(phils[3]), get_state(phils[4]));


    // if message is "hungry"
    if (msg.state == HUNGRY) {
        state_left = 0;
        state_right = 0;
        // check if chopsticks are available

        if (phils[(msg.index - 1)%PHIL_NO] == EATING) {
            state_left = 1;
        }

        if(phils[(msg.index + 1)%PHIL_NO] == EATING) {
            state_right = 1;
        }
        // if available...
        if (state_left+state_right == 0) {
            // send message EATING to node
            msg.state = EATING;
            write(node[msg.index][WRITE], &msg, sizeof(msg));
        } else {
            // make the node wait
            write(node[msg.index][WRITE], &msg, sizeof(msg));
        }
    } else if (msg.state == THINKING) {
        // awake neighborhood nodes to eat
        write(node[(msg.index-1)%PHIL_NO][WRITE], &msg, sizeof(msg));
        write(node[(msg.index+1)%PHIL_NO][WRITE], &msg, sizeof(msg));

    }
};

Edit: Oddly enough, when I run it in XTerm I can't see the extra character. I think that just means that XTerm doesn't display it. At this point, I'm pretty sure @Barmar is right in assuming it's one of my pipe write()s misbehaving.

Extra \1 Character In Printf

0 Answers