Machine: x86_64
OS: linux-gnu
Compiler: gcc
Compilation CFLAGS: -g -O2 -fdebug-prefix-map=/build/bash-2bxm7h/bash-5.0=.
-fstack-protector-strong -Wformat -Werror=format-security -Wall
-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 Versions: 3.2.57(1)-release, 5.0.3(1)-release, 5.1.0(1)-alpha
In order to reduce forks and make some tasks a lot quicker, I run
forked filters as background tasks, with dedicated I/O fd.
For sample, to convert human datetime to UNIX SECONDS, instead of running
_out=$(date -d "$_string" +%s)
many time in same script, I run something like:
_fifo=$(mktemp -u /tmp/fifo-XXXXXXXX)
mkfifo $_fifo
exec 9> >(exec stdbuf -o0 date -f - +%s >$_fifo 2>&1)
exec 8<$_fifo
rm $_fifo
Then to convert human datetime to UNIX SECONDS:
echo >&9 $_string
read -t 1 -u 8 _out
become a lot quicker!
But I recently discovered another way for this:
exec 8<> <(:)
exec 9> >(exec stdbuf -o0 date -f - +%s >&8 2>&8)
usable in same way:
echo >&9 $_string
read -t 1 -u 8 _out
maybe a little more quicker...
This was tested using https://f-hauri.ch/vrac/date1fork-demo.sh under
latest version of bash: 5.1.0(1), debian stable version: 5.0.3(1) and
old 3.2: 3.2.57(1).
There is maybe something to document or even create a new feature
about open2 and open3...
(I will have to rewrite https://f-hauri.ch/vrac/shell_connector.sh.txt ;)
--
Félix Hauri - <fe...@f-hauri.ch> - http://www.f-hauri.ch
