Configuration Information:
Machine: x86_64
OS: linux-gnu
Compiler: gcc
Compilation CFLAGS: -g -O2 -Wno-parentheses -Wno-format-security
uname output: Linux medium 4.19.0-9-amd64 #1 SMP Debian 4.19.118-2 (2020-04-29)
x86_64 GNU/Linux
Machine Type: x86_64-pc-linux-gnu
Bash Version: 5.1
Patch Level: 0
Release Status: rc1
Description:
Trying to see limits of timeout with `read -t`, I encounter strange
and unconstant result: sometime `read -t .000001` don't consider
timeout, when running fastly multiple time.
From help:
-t timeout time out and return failure... may be a fractional...
... exit status is greater than 128 if the timeout is exceeded.
Repeat-By:
$ read -t .0000001 foo ; echo $?
1
$ read -t .000001 foo ;echo $?
142
Ok, then microsecond seem to by smallest value.
$ tot=0; for i in {1..100} ;do
rt=${EPOCHREALTIME//.}
read -t .000001 foo
((tot+=${EPOCHREALTIME//.}-rt))
sleep .002
done; echo ${tot:: -2}.${tot: -2}
If this not end after 1 second, hit <return>, wait 1 second
and repeat (and count); You won't hit 100x <return>!
Maybe this return correctly after ~0.2 seconds. If yes, try
again. Mostly I have to hit 3 - 8x for this 100 loop test.
$ tot=0; for i in {1..100} ;do
rt=${EPOCHREALTIME//.}
read -t .000001 foo
((tot+=${EPOCHREALTIME//.}-rt))
done < <(
while :;do sleep 1;echo;done
);echo ${tot:: -2}.${tot: -2}
Correct output must be < 1000
--
Félix Hauri - <fe...@f-hauri.ch> - http://www.f-hauri.ch
