GoAWK seems to buffer more aggressively than (g)awk

[benhoyt]

For example, this script doesn't buffer in (g)awk: one is printed right away, then the sleep, then two. Whereas in GoAWK it buffers, so you see one\ntwo together after the sleep:

$ gawk 'BEGIN { print "one"; system("sleep 3"); print "two" }'

GoAWK waits because it uses buffered output by default. But the gawk docs indicate gawk buffers too. Is it because gawk doesn't buffer when writing directly to the TTY? But the same behavior seems to happen even when (g)awk output is redirected to a file, so I'm not sure.

[benhoyt]

Pushed some old work on this to the flush-better branch.

[xonixx]

Adding more info to this issue.

Simple script to test:

BEGIN {
  for (i=0; i<10; i++) {
    print i
    system("sleep 1")
    #fflush()
  }
}

I can confirm that gawk, bwk and mawk all output to console at real time (no buffering).
One can "fix" GoAWK by uncommenting the #fflush() line.

The existing buffering behavior can be problematic for some long-running scripts (my https://github.com/xonixx/makesure tool just one example) because it hides the progress of execution.