Request for command line flag to control line buffering

[unphased]

Similar to BSD Grep's --line-buffering flag.

For example I want to use ack to do a regex (which needs ack because regex has lookbehind) in a pipe with fswatch, the events trigger single lines of input over the pipe, so I'd like an immediate response, which buffers only lines.

[petdance]

I think you mean you want to disable line buffering, right?

[unphased]

Does it already do line buffering by default?

Edit: Wow, looks like it does! Okay!

Yes, then someone may want non-line-buffering as a feature. For performance. Or something. Hey Ack is supposed to be faster than grep, somehow, right?

Sorry about not properly testing. I thought i tested it right, but I didn't.

[petdance]

I'm confused when you say "I'd like an immediate response, which requires line buffering". "immediate response" would require a given program to not have any line buffering. An immediate response would mean that there is no buffer in the program for holding output.

[unphased]

Yes you are right, I edited a few things. Does it clarify? I'm 100% satisfied now because turns out ack already by default does not do buffering. Which is what I wanted to begin with.

Feel free to close, i'm leaving it because it could be a cool enhancement to add configurability w.r.t. buffering (but like i said I don't care much at this point).

What i meant by line buffering is simply to not engage in 4k-buffering (or page buffering). Perhaps in implementation that actually means no buffering, which is fine. I do believe a distinction does exist between completely raw no buffering and line-buffering (where a real buffer exists to hold data until a newline is seen), however. (the former not being advisable for performance reasons)

[petdance]

ack is written in Perl, and Perl by default does have output buffering on. We do have the --flush option to turn that off:

  --flush                       Flush output immediately, even when ack is used
                                non-interactively (when output goes to a pipe or
                                file).

How did you conclude that ack does not do buffering by default?

[unphased]

I see. I concluded as I did because the behavior between grep and ack is different. When used with a pipe, grep continues buffering, but ack is smart and figures out to use --flush in that situation.

Since you just showed me the flag, this answers the question. Thanks.