merging multiple input to same variable in bash script?

Question

I am trying to run a bash script that controls my fans based on hdd temp.

In the script I can add my fan to "ARRAY_FAN=/sys/class/hwmon/hwmon4/pwm6"

So I am wondering how I can add multiple fans to the ARRAY_FAN variable so when the script changes rmp on ARRAY_FAN it actually changes the rpm on all fans, pwm5,pwm6,pwm7 and pwm8

Can I add /sys/class/hwmon/hwmon4/pwm5 to pwm8 as individual variables, then add them to ARRAY_FAN, or add multiple lines to the ARRAY_FAN value?

This is the script I am trying to use https://github.com/kmwoley/unRAID-Tools/blob/master/unraid_array_fan.sh

Answer 1

For Bash version >= 4.0, you will find that an efficient way (of populating an array arr all at once) is to use the command mapfile, or its exact synonym readarray, as in:

mapfile -t arr < <(command)

Check your array content with $ declare -p arr and all available options and flags in your bash manual.

For example:

$ mapfile -t arr < <(seq 1 4)
$ declare -p arr
declare -a arr=([0]="1" [1]="2" [2]="3" [3]="4")

Expect this to fail in general if your command output contain globbing characters such as *. There are alternative ways of doing this here, an SO post by @gniourf_gniourf.

If your Bash version is older than 4.0, please indicate it for a solution not based on mapfile, along the line of:

IFS=$'\n' read -r -d $'\0' -a arr < <(command && printf '\0')