Pipe buffer size is 4k or 64k?

Question

I read in multiple places that the default buffer size for a pipe is 4kB (for instance, here), and my ulimit -a tends to confirm that statement:

Answer 1

It's programmable now

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As of Linux 2.6.35 you can use fcntl(2) with the F_SETPIPE_SZ operation to set the pipe buffer up to /proc/sys/fs/pipe-max-size. This is by default 1 MB; see proc(5).