raspi-config: warning: command substitution: ignored null byte in input

[Allan-N]

When exec'ing raspi-config (on a Pi Zero 2 W) I noticed the following warning message :

/usr/bin/raspi-config: line 43: warning: command substitution: ignored null byte in input

The simplest way I found to repro was to use bash -x raspi-config nonint do_finish

Reviewing the output you should see :

...
+ '[' -e /proc/device-tree/chosen/os_prefix ']'
++ cat /proc/device-tree/chosen/os_prefix
/usr/bin/raspi-config: line 43: warning: command substitution: ignored null byte in input
+ PREFIX=
...

The following output may also help :

$ od -xc /proc/device-tree/chosen/os_prefix
0000000    0000
         \0
0000001

[XECDesign]

Thanks