bash throwing "ignored null byte in input" warning in a script

By the way, if for whatever reason you need to keep the -print0 option of find (i.e you are expecting the results to contain new lines) you can do it at bash 4.4 with a different method and avoid results concatenation. Bash complains about null butes when this are assigned to variables , but null bytes at process substitution are handled without problems.

If you expect more than one results, you most probably need an array:

$ IFS= readarray -t -d '' array < <(find . -type f -name 'a*.sh' -print0)
$ declare -p array
declare -a array=([0]="./appslist.sh" [1]="./advfind2.sh" [2]="./autorotate.sh" [3]="./autorot.sh" [4]="./advfind.sh" [5]="./appslist(draft).sh")

If you expect just one result:

$ IFS= read -r -d '' var < <(find . -type f -name 'autorot.sh' -print0)
$ declare -p var
declare -- var="./autorot.sh"

Just for the record, this null bytes dropping behavior does not apply in other shells like zsh. Your command will work in zsh even with more than one results using -print0 without problem.

zsh$ var=$(find . -type f -name 'auto*.sh' -print0)
zsh$ declare -p var                                
typeset var=$'./autorotate.sh\C-@./autorot.sh\C-@'
zsh$ echo "$var" |od -w32 -t x1c                   
0000000  2e  2f  61  75  74  6f  72  6f  74  61  74  65  2e  73  68  00  2e  2f  61  75  74  6f  72  6f  74  2e  73  68  00  0a
          .   /   a   u   t   o   r   o   t   a   t   e   .   s   h  \0   .   /   a   u   t   o   r   o   t   .   s   h  \0  \n

Your command would be unchanged (even it's invalid syntax in your question, maybe copy-paste issue) and will work the same in bash 4.3 and bash 4.4.

The null byte is still dropped, the only different is warning message, which was added in bash 4.4 patch 2

In your case, the command works because it found only one entry. If multiple entries found, then they would be concatenated together (because null byte was dropped).

Change the command to:

FIND_RPM=$(find /opt/RPM/components -type d -name enum-1.1.6)

fix that issue, but still choke if any path contains newline character.

FIND_RPM=find /opt/RPM/components -type d -name enum-1.1.6 -print0

should probably be

FIND_RPM=$(find /opt/RPM/components -type d -name enum-1.1.6 -print0)

But that's not the cause of the warning message.

You're using -print0 with find which will output a nul byte ($'\0', ASCII 0) as separator between the paths found by find instead of the usual newline generated by -print (without the zero).

One usually uses -print0 to send paths that may contain spaces or other whitespace characters off to xargs or other utilities that knows how to handle nul-byte-terminated paths. This is so that exotic filenames in paths may be correctly handled (the nul byte may not be part of a filename on Unix, but a space or newline may be).

In your case, I think it's just a matter of changing -print0 to -print.

This also has the effect of giving you valid paths in the case where multiple paths are found. With -print0, Bash would drop the nul and concatenate the paths.