# Nonblocking IO read **URL:** \ **Category:** Ruby\ **Created:** [November 7, 2006, 10:50am UTC](https://www.ruby-forum.com/t/nonblocking-io-read/74621 "2006-11-07T10:50:22Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![robertjames](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/e9c0ed/32.png) [@robertjames](https://www.ruby-forum.com/u/robertjames)\ **Post date:** [November 7, 2006, 10:50am UTC](https://www.ruby-forum.com/t/nonblocking-io-read/74621/1 "2006-11-07T10:50:22Z")
How can I perform a nonblocking IO read? That is, read whatever is there to read and return. If there’s nothing yet, just return. Failing that, is there a way to manually check if there’s anything to read or the read will block? (Note that I’m developing for both 'nix and Windows.) ---
**Author:** ![robertjames](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/e9c0ed/32.png) [@robertjames](https://www.ruby-forum.com/u/robertjames)\ **Post date:** [November 7, 2006, 10:50am UTC](https://www.ruby-forum.com/t/nonblocking-io-read/74621/2 "2006-11-07T10:50:25Z")
On Wed, 1 Nov 2006 removed\_email\_address@domain.invalid wrote: > How can I perform a nonblocking IO read? That is, read whatever is > there to read and return. If there’s nothing yet, just return. > > Failing that, is there a way to manually check if there’s anything to > read or the read will block? > > (Note that I’m developing for both 'nix and Windows.) it can’t be done. search the archives, this sort of thing almost always indicates a design flaw. for instance - what will your program do if there is no input? regards. -a ---
**Author:** ![robertjames](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/e9c0ed/32.png) [@robertjames](https://www.ruby-forum.com/u/robertjames)\ **Post date:** [November 7, 2006, 10:50am UTC](https://www.ruby-forum.com/t/nonblocking-io-read/74621/3 "2006-11-07T10:50:29Z")
On Oct 31, 2006, at 6:23 PM, removed\_email\_address@domain.invalid wrote: > On Wed, 1 Nov 2006 removed\_email\_address@domain.invalid wrote: > > > How can I perform a nonblocking IO read? That is, read whatever > > is there to read and return. If there’s nothing yet, just return. That’s what the Unix read() function does (“man 2 read”), available in Ruby as IO#sysread(). The ri documentation doesn’t explain much about how to use Ruby’s sysread, unfortunately. > > Failing that, is there a way to manually check if there’s anything > > to read or the read will block? > > > > (Note that I’m developing for both 'nix and Windows.) The select() function (Kernel#select, in Ruby) is the standard way to do IO multiplexing under Unix. You give it a list of file handles on which you’re waiting to be able to read or write, and it returns when one or more of them is ready. Windows provides a select() function, too, but it only supports sockets (not pipes or ordinary file IO.) The Win32 API generally doesn’t provide non-blocking IO methods, because it’s assumed you’ll use threads if you want to do something else while waiting for IO. > it can’t be done. search the archives, this sort of thing almost > always > indicates a design flaw. for instance - what will your program do > if there is > no input? Check other IO channels, wait for other sorts of events, do work - whatever. Where do come from asserting that the use of non-blocking IO represents a “design flaw”? Tom ---
**Author:** ![robertjames](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/e9c0ed/32.png) [@robertjames](https://www.ruby-forum.com/u/robertjames)\ **Post date:** [November 7, 2006, 10:50am UTC](https://www.ruby-forum.com/t/nonblocking-io-read/74621/4 "2006-11-07T10:50:33Z")
In the interests of promoting creativity, I’ll ask the question without any prior assumptions: I’m using popen4 (great gem, btw) to run an external command and capture stdout and stderr. If one (or both) of those is empty, I don’t want to hang. Just keep on moving. In fact, stderr will normally be empty. How could I do this? (I’m supporting 'nix and Windows) ---
**Author:** ![robertjames](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/e9c0ed/32.png) [@robertjames](https://www.ruby-forum.com/u/robertjames)\ **Post date:** [November 7, 2006, 10:50am UTC](https://www.ruby-forum.com/t/nonblocking-io-read/74621/5 "2006-11-07T10:50:31Z")
removed\_email\_address@domain.invalid wrote: > it can’t be done. search the archives, this sort of thing almost always > indicates a design flaw. for instance - what will your program do if there is > no input? I’m running an external command (using popen4 - yes, it is available on Windows also). I capture stdout and stderr. “what will your program do if there is no input?” - I assume you mean output - Well, I hope there is no stderr output. If there is, I’d like to capture it and feed it to Logger. Likewise, if there is a problem, and there’s no stdout, then I don’t want to wait for ever - I want to throw an exception. ---
**Author:** ![robertjames](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/e9c0ed/32.png) [@robertjames](https://www.ruby-forum.com/u/robertjames)\ **Post date:** [November 7, 2006, 10:50am UTC](https://www.ruby-forum.com/t/nonblocking-io-read/74621/6 "2006-11-07T10:50:37Z")
On Wed, 1 Nov 2006 removed\_email\_address@domain.invalid wrote: > I’m running an external command (using popen4 - yes, it is available on > Windows also). I capture stdout and stderr. “what will your program do if > there is no input?” - I assume you mean output - Well, I hope there is no > stderr output. If there is, I’d like to capture it and feed it to Logger. > > Likewise, if there is a problem, and there’s no stdout, then I don’t want to > wait for ever - I want to throw an exception. so, basically you want to timeout on a read right? in unix you can just use require ‘timeout’ Timeout::timeout(n) do Open4.popen4 … … … end but, this is implimented via a thread so i think the read is going to block your entire process in windows… you might try it. -a ---
**Author:** ![robertjames](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/e9c0ed/32.png) [@robertjames](https://www.ruby-forum.com/u/robertjames)\ **Post date:** [November 7, 2006, 10:50am UTC](https://www.ruby-forum.com/t/nonblocking-io-read/74621/7 "2006-11-07T10:50:36Z")
On Wed, 1 Nov 2006, Tom P. wrote: > On Oct 31, 2006, at 6:23 PM, removed\_email\_address@domain.invalid wrote: > > > On Wed, 1 Nov 2006 removed\_email\_address@domain.invalid wrote: > > > > > How can I perform a nonblocking IO read? That is, read whatever is there > > > to read and return. If there’s nothing yet, just return. > > That’s what the Unix read() function does (“man 2 read”), available in Ruby > as IO#sysread(). The ri documentation doesn’t explain much about how to use > Ruby’s sysread, unfortunately. no, that blocks. try this: harp:~ \> ruby -e ‘STDIN.sysread(1)’ it blocks. the OP wants a non-blocking call. eg harp:~ \> ruby -r io/nonblock -e ‘STDIN.nonblock{ STDIN.sysread(1) }’ -e:1:in `sysread': Resource temporarily unavailable (Errno::EAGAIN) from -e:1 from /home/ahoward//lib/ruby/1.8/io/nonblock.rb:19:in`nonblock’ from -e:1 > The select() function (Kernel#select, in Ruby) is the standard way to do IO > multiplexing under Unix. You give it a list of file handles on which you’re > waiting to be able to read or write, and it returns when one or more of them > is ready. Windows provides a select() function, too, but it only supports > sockets (not pipes or ordinary file IO.) The Win32 API generally doesn’t > provide non-blocking IO methods, because it’s assumed you’ll use threads if > you want to do something else while waiting for IO. right. but ruby’s thread are green and, on windows, block the entire process when waiting on IO so not an option here. > Check other IO channels, wait for other sorts of events, do work - whatever. > Where do come from asserting that the use of non-blocking IO represents a > “design flaw”? because nine times out of ten code has nothing to do if no input is available. if it does that’s another story, but then there are basically two options: - use select or an event abstraction in one giant loop. if you do this you are going to block anyhow, only based on all inputs, not just one. - use threads, only you can’t if you’re wanting ruby code to run nb in windows. i’m not saying there is never a case for nbio - i use it myself - just that, unless a developer has a good reason to be doing something else it’s not required and, as a search of ruby-talk will show, that is often the case. regards. -a ---
**Author:** ![robertjames](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/e9c0ed/32.png) [@robertjames](https://www.ruby-forum.com/u/robertjames)\ **Post date:** [November 7, 2006, 10:50am UTC](https://www.ruby-forum.com/t/nonblocking-io-read/74621/8 "2006-11-07T10:50:47Z")
On Oct 31, 2006, at 5:30 PM, S. Robert J. wrote: > Not very attractive… > > Back to the original question: there is no simple way to read > nonblocking, or see if any output is available ?!?! in io/wait: — IO#ready? returns non-nil if input available without blocking, or nil. also: ri IO.read\_nonblock ---
**Author:** ![robertjames](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/e9c0ed/32.png) [@robertjames](https://www.ruby-forum.com/u/robertjames)\ **Post date:** [November 7, 2006, 10:50am UTC](https://www.ruby-forum.com/t/nonblocking-io-read/74621/9 "2006-11-07T10:50:48Z")
[removed\_email\_address@domain.invalid] | | it can’t be done. search the archives, this sort of thing almost | always indicates a design flaw. for instance - what will your | program do if there is no input? nonblocking IO is not a design-flaw; it is something that is in common use and is supported by most languages with a decent socket API. on some OS’es this is even available for file IO (although widespread language support seems to lag behind). Java for example got proper nonblocking socket IO in 1.4 (see JSR-000051 “New I/O APIs for the JavaTM Platform”). for examples of use you might want to check out the Reactor pattern and other patterns for concurrent programming. -Bjørn ---
**Author:** ![robertjames](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/e9c0ed/32.png) [@robertjames](https://www.ruby-forum.com/u/robertjames)\ **Post date:** [November 7, 2006, 10:50am UTC](https://www.ruby-forum.com/t/nonblocking-io-read/74621/10 "2006-11-07T10:50:43Z")
Not very attractive… Back to the original question: there is no simple way to read nonblocking, or see if any output is available ?!?! ---
**Author:** ![robertjames](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/e9c0ed/32.png) [@robertjames](https://www.ruby-forum.com/u/robertjames)\ **Post date:** [November 7, 2006, 10:50am UTC](https://www.ruby-forum.com/t/nonblocking-io-read/74621/11 "2006-11-07T10:50:48Z")
On Oct 31, 2006, at 7:20 PM, removed\_email\_address@domain.invalid wrote: > How could I do this? > Have you tried simply reading from them? When the command > terminates, that should close those pipes on the command’s end. At > that point, a simple read on the stdout handle, for instance, will > return whatever output there was and then eof. If there’s no output, > the read should return immediately. Did you try that yet? Did you > try the (Windows-oriented) example from the ‘ri Open4’ page? If > you’re working in Unix you could try status = POpen4::poen4(‘cat -’) do |stdout, stderr, stdin| stdin.puts ‘hello world’ stdin.close puts “stdout: #{stdout.read.strip}” puts “stderr: #{stderr.read.strip}” end Anyway, you would only need nonblocking IO if you wanted to read bits of the stderr stream before the command exited, but that doesn’t sound like what you’re want. Tom ---
**Author:** ![robertjames](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/e9c0ed/32.png) [@robertjames](https://www.ruby-forum.com/u/robertjames)\ **Post date:** [November 7, 2006, 10:50am UTC](https://www.ruby-forum.com/t/nonblocking-io-read/74621/12 "2006-11-07T10:50:50Z")
On Wed, 1 Nov 2006, Tom P. wrote: > The select() function (Kernel#select, in Ruby) is the standard way to do IO > multiplexing under Unix. At a very deep level (last time I looked) thread animation and IO met and became the same thing in a giant select lurking in the core of the ruby Interpreter. ie. Use select / spin another thread amounted cosmically to the same thing. Choose whatever is easiest for you. John C. Phone : (64)(3) 358 6639 Tait Electronics Fax : (64)(3) 359 4632 PO Box 1645 Christchurch Email : removed\_email\_address@domain.invalid New Zealand “We have more to fear from The Bungling of the Incompetent Than from the Machinations of the Wicked.” (source unknown) ---
**Author:** ![robertjames](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/e9c0ed/32.png) [@robertjames](https://www.ruby-forum.com/u/robertjames)\ **Post date:** [November 7, 2006, 10:50am UTC](https://www.ruby-forum.com/t/nonblocking-io-read/74621/13 "2006-11-07T10:50:49Z")
On Oct 31, 2006, at 9:37 PM, Tom P. wrote: > If you’re working in Unix you could try > > status = POpen4::poen4(‘cat -’) do |stdout, stderr, stdin| D’oh! (typo) That should have been status = POpen4::popen4(‘cat -’) do |stdout, stderr, stdin| stdin.puts ‘hello world’ stdin.close puts “stdout: #{stdout.read.strip}” puts “stderr: #{stderr.read.strip}” end Tom ---
**Author:** ![robertjames](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/e9c0ed/32.png) [@robertjames](https://www.ruby-forum.com/u/robertjames)\ **Post date:** [November 7, 2006, 10:50am UTC](https://www.ruby-forum.com/t/nonblocking-io-read/74621/14 "2006-11-07T10:50:50Z")
[Tom P. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)] | | The select() function (Kernel#select, in Ruby) is the standard way to | do IO multiplexing under Unix. You give it a list of file handles on | which you’re waiting to be able to read or write, and it returns when | one or more of them is ready. Windows provides a select() function, | too, but it only supports sockets (not pipes or ordinary file IO.) if memory serves, a select(2) on a file descriptors representing a (disk) file only had defined semantics when used to wait on mandatory locking and is not used for ensuring that a read(2) or write(2) will not block. (I might be in error since it has been a while since I looked into it). -Bjørn ---
**Author:** ![robertjames](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/e9c0ed/32.png) [@robertjames](https://www.ruby-forum.com/u/robertjames)\ **Post date:** [November 7, 2006, 10:50am UTC](https://www.ruby-forum.com/t/nonblocking-io-read/74621/15 "2006-11-07T10:50:52Z")
On Wed, 1 Nov 2006, Bjorn B. wrote: > Java for example got proper nonblocking socket IO in 1.4 (see > JSR-000051 “New I/O APIs for the JavaTM Platform”). but it’s archaic compared to event driven frameworks like [libevent](http://www.monkey.org/~provos/libevent/) [http://liboop.ofb.net/](http://liboop.ofb.net/) in addition it’s a hack in the c lib of many oses. > for examples of use you might want to check out the Reactor pattern > and other patterns for concurrent programming. afaik the reactor pattern is a synchronous pattern [artima - Comparing Two High-Performance I/O Design Patterns](http://www.artima.com/articles/io_design_patterns2.html) not unlike the model of libevent and liboop - which are both synchronous… am i missing something? -a ---
**Author:** ![robertjames](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/e9c0ed/32.png) [@robertjames](https://www.ruby-forum.com/u/robertjames)\ **Post date:** [November 7, 2006, 10:50am UTC](https://www.ruby-forum.com/t/nonblocking-io-read/74621/16 "2006-11-07T10:50:58Z")
On 10/31/06, removed\_email\_address@domain.invalid [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > Are you having an interactive conversation with the process created by popen4? Is that why you need nbio, because you need to poll more than one stream simultaneously? You can get the file descriptors associated with stdout and stderr (they’ll be 1 and 2 unless you did something unusual), set them nonblocking, and select them for reading with a short timeout. ---
**Author:** ![robertjames](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/e9c0ed/32.png) [@robertjames](https://www.ruby-forum.com/u/robertjames)\ **Post date:** [November 7, 2006, 10:51am UTC](https://www.ruby-forum.com/t/nonblocking-io-read/74621/17 "2006-11-07T10:51:00Z")
On 10/31/06, removed\_email\_address@domain.invalid [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > > use and is supported by most languages with a decent socket API. on > > some OS’es this is even available for file IO (although widespread > > language support seems to lag behind). > > > > Java for example got proper nonblocking socket IO in 1.4 (see > > JSR-000051 “New I/O APIs for the JavaTM Platform”). > > but it’s archaic compared to event driven frameworks like Ara, I’m curious to know why you think the usage of nbio is archaic or indicative of a design flaw. I wrote the EventMachine library in order to make certain kinds of Ruby programs easier to write, and it uses nbio pervasively. I’m fairly sure libevent does, also. EM works with almost any kind of descriptor, except for certain things on Windows (like \_pipe() descriptors, which are nonselectable, and some of the native Windows objects that don’t support a socket-like API). Up until recently (late May 2006), Ruby didn’t have complete support for nbio on all descriptor types, which is one of the reasons that EventMachine includes a compiled C++ extension. EM interoperates perfectly well with Ruby threads,\* which is another important reason to use nbio. * * * \*Except for certain cases on Windows where Ruby code that accesses standard descriptors blocks all other Ruby threads. But this is not an EM issue, ---
**Author:** ![robertjames](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/e9c0ed/32.png) [@robertjames](https://www.ruby-forum.com/u/robertjames)\ **Post date:** [November 7, 2006, 10:51am UTC](https://www.ruby-forum.com/t/nonblocking-io-read/74621/18 "2006-11-07T10:51:05Z")
On 11/1/06, removed\_email\_address@domain.invalid [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > ready so i… oops, now it is ready), and stdio buffers being lost. > > - something else could simoultaneously be done, but the problem could > > [http://groups-beta.google.com/group/comp.lang.ruby/browse\_frm/thread/116231c43621a61b/775af5d9900aa716?lnk=gst&q=non+blocking+io&rnum=6#775af5d9900aa716](http://groups-beta.google.com/group/comp.lang.ruby/browse_frm/thread/116231c43621a61b/775af5d9900aa716?lnk=gst&q=non+blocking+io&rnum=6#775af5d9900aa716) > > his insight is enough to raise ‘too low-level’ warnings in my mind! at > least > until using nbio from a ruby script doesn’t require such deep > understanding of > ruby’s internals Thanks for clarifying, Ara. Having put a lot of work into domesticating nbio for Ruby programs, all I can say is I agree with you. I still don’t feel like I understand what the OP really is trying to do. Feels like it shouldn’t be such a hard problem. Maybe nbio is just a red herring in this case (although it does appear in the first sentence of the OP). ---
**Author:** ![robertjames](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/e9c0ed/32.png) [@robertjames](https://www.ruby-forum.com/u/robertjames)\ **Post date:** [November 7, 2006, 10:51am UTC](https://www.ruby-forum.com/t/nonblocking-io-read/74621/19 "2006-11-07T10:51:05Z")
On Wed, 1 Nov 2006, Francis C. wrote: > includes a compiled C++ extension. EM interoperates perfectly well with Ruby > threads,\* which is another important reason to use nbio. hi francis- it’s exactly things like eventmachine that make me say using nbio is archaic - i don’t need to handle the complexities of nbio when powerful abstractions like it exist! for instance, consider the OP’s orignial question: basically he wanted to timeout if stdout was not produced in a certain amount of time. i certainly wouldn’t delve into the complexities of nbio to handle this, but instaed might do something along the lines of harrp:~ \> cat a.rb require ‘open4’ and require ‘timeout’ def might\_take\_too\_long cmd, stdin, timeout = 42 stdout, stderr = ‘’, ‘’ Timeout::timeout(timeout) do open4.popen4(cmd) do |cid,i,o,e| i.write stdin and i.close o.each{|line| stdout \<\< line} and e.each{|line| stderr \<\< line} end end [stdout, stderr] end p might\_take\_too\_long(‘ruby’, ‘sleep 1 and p 42’, 2) p might\_take\_too\_long(‘ruby’, ‘sleep 42 and p 42’, 2) harp:~ \> ruby a.rb [“42\n”, “”] /home/ahoward//lib/ruby/1.8/timeout.rb:43:in `might\_take\_too\_long’: execution expired (Timeout::Error) now, timeout might use any manner of select and/or nbio - i don’t care. my point is just that, for 90-99% of the problems seem to want to solve with nbio, it is way too low level a mechanism to skin the cat and prefer to stand on the shoulders of powerful abstractions, like eventmachine or threads or whatever, and avoid the painful details of EAGAIN, race conditions (it wasn’t ready so i… oops, now it is ready), and stdio buffers being lost. for the record, i have code which uses nbio, io/nonblock, etc. it’s simply my observation that a majority of the posts to this list about nbio have two issues: - nothing else can really be done while waiting for io. eg. nbio isn’t needed for the problem at hand - something else could simoultaneously be done, but the problem could be more elegantly solved with threads, queues, readpartial, or something even more abstract the rest, of course, really do need nbio. a quick search of archives though is an eye opener into the difficulties of mixing nbio and stdio, check out these threads, specifically the posts by tanaka akira, who knows about 10 billion times more about nbio and ruby than i do [http://groups-beta.google.com/group/comp.lang.ruby/browse\_frm/thread/47b0e296cbe9c410/23e22cc9e56a3200?lnk=gst&q=non+blocking+io&rnum=1#23e22cc9e56a3200](http://groups-beta.google.com/group/comp.lang.ruby/browse_frm/thread/47b0e296cbe9c410/23e22cc9e56a3200?lnk=gst&q=non+blocking+io&rnum=1#23e22cc9e56a3200) [http://groups-beta.google.com/group/comp.lang.ruby/browse\_frm/thread/116231c43621a61b/775af5d9900aa716?lnk=gst&q=non+blocking+io&rnum=6#775af5d9900aa716](http://groups-beta.google.com/group/comp.lang.ruby/browse_frm/thread/116231c43621a61b/775af5d9900aa716?lnk=gst&q=non+blocking+io&rnum=6#775af5d9900aa716) [http://groups-beta.google.com/group/comp.lang.ruby/browse\_frm/thread/116231c43621a61b/775af5d9900aa716?lnk=gst&q=non+blocking+io&rnum=6#775af5d9900aa716](http://groups-beta.google.com/group/comp.lang.ruby/browse_frm/thread/116231c43621a61b/775af5d9900aa716?lnk=gst&q=non+blocking+io&rnum=6#775af5d9900aa716) [http://groups-beta.google.com/group/comp.lang.ruby/browse\_frm/thread/116231c43621a61b/775af5d9900aa716?lnk=gst&q=non+blocking+io&rnum=6#775af5d9900aa716](http://groups-beta.google.com/group/comp.lang.ruby/browse_frm/thread/116231c43621a61b/775af5d9900aa716?lnk=gst&q=non+blocking+io&rnum=6#775af5d9900aa716) his insight is enough to raise ‘too low-level’ warnings in my mind! at least until using nbio from a ruby script doesn’t require such deep understanding of ruby’s internals kind regards. -a ---
**Author:** ![robertjames](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/e9c0ed/32.png) [@robertjames](https://www.ruby-forum.com/u/robertjames)\ **Post date:** [November 7, 2006, 10:52am UTC](https://www.ruby-forum.com/t/nonblocking-io-read/74621/20 "2006-11-07T10:52:13Z")
Tom P. wrote: > Anyway, you would only need nonblocking IO if you wanted to read bits of > the stderr stream before the command exited, but that doesn’t sound like > what you’re want. Actually this is not correct: if there is a lot written to stderr then you need to read that concurrently. If you do not do that then the process will block on some stderr write operation that fills up the pipe and you get a deadlock because your code waits for process termination. Kind regards ``` robert ``` [Next page](https://www.ruby-forum.com/t/nonblocking-io-read/74621.md?page=2)