By default, is STDOUT unbuffered? If not what is the type of its default buffering
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- 2In what language/environment?Karl Knechtel– Karl Knechtel2010-12-29 07:06:07 +00:00Commented Dec 29, 2010 at 7:06
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2 Answers
You didn't give a language, but assuming that you're using C's stdio functions (fopen() etc.) or a language that uses these (and most do, for portability reasons):
It depends on the underlying C runtime library.
Most libraries will try to detect whether STDOUT is connected to a terminal, and avoid buffering if so, and perform block buffering (e.g. my Linux system buffers 8Kb at a time) if not.
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ShadowRanger
Pretty sure this is wrong;
stdout is typically line-buffered when connected to a terminal, not unbuffered. When all your outputs end in a newline, the difference is irrelevant, but if you're outputting without newlines (say, showing a "progress bar" by outputting a dot at a time), it will be buffered. Explicit calls to fflush would be needed to output partial lines on demand, or you'd use setvbuf to change the buffering mode for the FILE* in general.
j_random_hacker
@ShadowRanger: You're right, please edit to add this.
Short Answer: By default STDOUT is usually unbuffered. If this is a problem for you, there is fflush(stdout); but that is rarely needed
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ShadowRanger
Again, as noted on accepted answer,
stdout is typically line buffered when connected to a terminal, and block buffered otherwise. No common C runtime I'm aware of makes it unbuffered by default.