Is there a way to ensure copy-port is unbuffered? I am seeing processes dying due to error without any output through copy-port, output comes all in one chunk when the process finishes successfully.

I am actually looking at the code of copy-port and it doesn’t seem like its buffering anything which is all the more strange. :confused:

@pocmatos Many ports are buffered by default, and it looks like copy-port never calls flush-output. One option is to set the buffer mode of the output ports to unbuffered and use the existing copy-port; another is to make your own copy-port that calls flush-output. (Seems like it would be useful to add a #:flush? option to copy-port too.)

@ryanc I have defined my own copy-port for now with flushing enabled. I will send a PR.

Hi there! I am using the code below to append strings to a file: (define (save-string str) (write (string-append str "\n") (open-output-file data-file #:exists 'append #:mode 'text)) ) But here is what I get: one two three "foo bar\n" where "foo bar\n" was added by save-string. What I want is a file that looks like

one
two
three
foo bar

(with a new-line at the end)

@jxxcarlson You are getting that because you are using write.

https://docs.racket-lang.org/reference/Writing.html?q=write#%28def._%28%28quote._~23~25kernel%29._write%29%29

Write behaves like that because cores instances need to able to be read back in.

Try for your case fprintf on the output-port and then don’t forget to close it.

or even better use with-output-to-file which automatically closes the port:

https://docs.racket-lang.org/reference/file-ports.html?q=with-output-to-file#%28def._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._with-output-to-file%29%29