CODEWITHSUNDEEP
cprintf
ankush981
ankush981

Reputation: 5417

Is adding the newline character to printf() equivalent to flushing the stream?

The following program shows how buffered I/O can cause problems in programs when errors like 'divide by zero' happen:

int main()
{
    int a = 1, b = 0, c;

    printf("Dividing...");
    c = a/b;

    printf("Answer is: %d\n", c);
    return 0;
}

The output is Floating point exception (core dumped).

Fair enough. But surprisingly, if I changed the first printf to printf("Dividing...\n");, this text actually gets printed before the program crashes (I'm running GCC on Linux, by the way).

Am I to conclude that adding a newline is equivalent to flushing? And if so, if all my printf() strings end in \n, I'm actually depriving myself of the benefits of buffered I/O?

Upvotes: 3

Views: 519

Answers (1)

SzG
SzG

Reputation: 12629

If your standard output is going to a terminal, yes, it's equal to flushing, as printf() will use line-based buffering.

If it's redirected to a file, then no. In this case printf() uses much bigger buffers, usually corresponding to file system block sizes or whatever, to optimize IO.

Upvotes: 4

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