How adding a New line in print statement can change way of output?

Question

In a for loop, if i am adding new line then it is printing at each iteration, And if i am just giving comma, means i want to print count down in one line, then it is waiting for completion of for loop. Which part i am missing?

Following code will print the latest count down after every iteration completed (because of '\n')

#include <stdio.h>

int main () {
    int x;
    for (x =0; x< 10; x++) {
        printf("%d\n", x);
        sleep(1);
    }
    printf("Fire!\n");
    return 1;
}

Following code will not print the latest count down, but will print when everything is done (may be because of ',')

#include <stdio.h>

int main () {
    int x;
    for (x =0; x< 10; x++) {
        printf("%d, ", x);
        sleep(1);
    }
    printf("Fire!\n");
    return 1;
}

A buffer is used to reduce calling times and make the program more efficient. — , Sep 16 '13 at 05:39

score 2 · Accepted Answer · answered Sep 16 '13 at 05:37

2

You can flush the stdout buffer explicitly:

for (x =0; x< 10; x++) {
    printf("%d, ", x);
    fflush(stdout);
    sleep(1);
}

answered Sep 16 '13 at 05:37

Yu Hao

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thanks. works perfectly fine – Vishwadeep Singh Sep 16 '13 at 05:39

score 2 · Answer 2 · answered Sep 16 '13 at 05:37

2

Your guess in the comment is correct, it's because output is buffered. If you want the output immediately then you have to flush the buffers with the fflush function after printf.

answered Sep 16 '13 at 05:37

Some programmer dude

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thanks. works perfectly fine – Vishwadeep Singh Sep 16 '13 at 05:39
just one query @JoachimPileborg , Why "\n" is working fine? Is new line make the buffers to flush? – Vishwadeep Singh Sep 16 '13 at 05:42
2

@Vishwadeep Yes, `stdout` is line buffered if it's connected to a terminal. – Yu Hao Sep 16 '13 at 05:43
@Vishwadeep Yes, the newline flushes the buffer. – 0decimal0 Sep 16 '13 at 06:06

How adding a New line in print statement can change way of output?

2 Answers2