为什么 printf 在调用之后不会刷新，除非换行符是格式化的字符串？

Question

Why does printf not flush after the call unless a newline is in the format string? Is this POSIX behavior? How might I have printf immediately flush every time?

转载于:https://stackoverflow.com/questions/1716296/why-does-printf-not-flush-after-the-call-unless-a-newline-is-in-the-format-strin

Answer 1

The stdout stream is buffered, so will only display what's in the buffer after it reaches a newline (or when it's told to). You have a few options to print immediately:

Print to stderr instead using fprintf:

fprintf(stderr, "I will be printed immediately");

Flush stdout whenever you need it to using fflush:

printf("Buffered, will be flushed");
fflush(stdout); // Will now print everything in the stdout buffer

Edit: From Andy Ross's comment below, you can also disable buffering on stdout by using setbuf:

setbuf(stdout, NULL);