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Re: read with very small timeout sometime hand on stdin


From: felix
Subject: Re: read with very small timeout sometime hand on stdin
Date: Sun, 1 Nov 2020 10:29:11 +0100
User-agent: Mutt/1.10.1 (2018-07-13)

On Thu, Oct 29, 2020 at 01:57:33PM +0100, felix wrote:
> > I can't reproduce this using the following stripped-down reproducer:

Sorry to insist, but... This is not easy because not constant.

For this, I wrote a little script tested on several host, then searching
for installation that was not mine... Tested at https://www.jdoodle.com/ia/3EO

  $ sed <<"eotest" >/tmp/test-timeout-race.sh 's/^    //'
    #!/bin/bash
    
    declare -p BASH_VERSI{NFO,ON}
    uptime
    uname -a
    
    po() {
        for f in {1..10000};do
            read -t .000001 v
            rc=$?
            [ $rc -ne 142 ] || [ "$v" ] &&
                echo f:$f, v:$v, RC:$rc.
            done < <(
                for i in {1..10000};do sleep 3;echo Timed;done
                )
    }
    
    exec 2>&1
    TIMEFORMAT="U:%U S:%S R:%R"
    for test in {1..20};do
        time po
    done
eotest

If first test don't show strange** output, run test again.
 (** lines begining by `f:`)

-- 
 Félix Hauri  -  <felix@f-hauri.ch>  -  http://www.f-hauri.ch



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