Hi Greg/Chet Ramey,
Thank you so much for the response! It gave me an idea on what has to be done
next.
We have been using the same script all these years and had no issues of broken
commands when used with the lower versions of bash which is why I have been
thinking whether to rewrite the script for the new bash(4.4) or edit the bash
source.
The reason behind using -print0 is to use the resultant output to find a binary
Below are the lines of code followed by the find command:
FIND_RPM="$(find $linIdx -type d -name "${2}" -print0 2>/dev/null)"
[ -n "$FIND_RPM" ] && \
[ -s "${FIND_RPM}/bin" ] && \
bdt_msg 4 "[D] Found %s in %s component area." "$2" "$linIdx" && \
...
...
>> If you want to suppress the warning, you'll have to edit the source and
>> rebuild.
Do you have a guide on how to do this?
Or else I have been planning to add tr to remove the nuls as suggested by Greg.
Regards,
Emlyn Jose.
---------------------------------------------------------------------------------------------------------
-----Original
Message-------------------------------------------------------------------------------
From: Chet Ramey [mailto:[email protected]]
Sent: Saturday, April 8, 2017 7:48 AM
To: Emlyn Jose (GIS); [email protected]
Cc: [email protected]
Subject: Re: bash 4.4 null byte warning!!
On 4/6/17 3:47 AM, [email protected] wrote:
> Hi,
>
>
>
> We are trying to use the bash 4.4 downloaded from
> http://ftp.gnu.org/gnu/bash/ on our RHEL 6.2 machine.
>
> But while using a script that has this command :
>
> FIND_RPM=`find /opt/RPM/components -type d -name enum-1.1.6-print0`
>
> It throws a warning as below:
>
> bash:warning:command substitution:ignored null byte ininput
Yes. It drops the null bytes because C strings can't handle them. I received
bug reports asking why bash silently transforms the command substitution output
and added the warning while not changing the behavior.
If you want to suppress the warning, you'll have to edit the source and rebuild.
This does beg the question of why you're using -print0 without something on the
receiving end to handle the null bytes.
--
``The lyf so short, the craft so long to lerne.'' - Chaucer
``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, UTech, CWRU [email protected] http://cnswww.cns.cwru.edu/~chet/
--------------------------------------------------------------------------------------------------------------------------------
-----Original
Message------------------------------------------------------------------------------------------------------
From: Greg Wooledge [mailto:[email protected]]
Sent: Thursday, April 6, 2017 8:15 PM
To: Emlyn Jose (GIS)
Cc: [email protected]
Subject: Re: bash 4.4 null byte warning!!
On Thu, Apr 06, 2017 at 07:47:35AM +0000,
[email protected]<mailto:[email protected]> wrote:
> FIND_RPM=`find /opt/RPM/components -type d -name enum-1.1.6 -print0`
> It throws a warning as below:
>
> bash: warning: command substitution: ignored null byte in input
Your command is broken, and bash is warning you of this. Why do you want to
silence the warning instead of fixing the command?
If your find returns a single result, you get a filename followed by NUL, and
the NUL is discarded, leaving you a filename inside the command substitution
(and therefore the variable). You could achieve the EXACT same result by
dropping the -print0. Then, if you get a single result from find, you get the
filename followed by newline, and the command substitution discards the
trailing newline, leaving you just the filename in the command substitution and
therefore the variable.
On the other hand, if your find command returns MULTIPLE results, then you have
file1\000file2\000 and the command substitution drops the NUL bytes, leaving
you with file1file2 in your variable. At least if you dropped the -print0 you
would have file1\nfile2 in your variable, which is still wrong, but not as
wrong as file1file2.
> Is there any patch available for this or is there any way to make bash
> silently drop this warning(which has been the behavior on the lower versions
> of bash)??
If you REALLY want to continue to run a broken command, you can explicitly use
tr to remove the NULs before the command substitution ever sees them.
var=$(find ... -print0 | tr -d '\0')
That will prevent the warning and allow you to continue running a broken script
without letting your coworkers catch on to the bugs (or whatever your issue
with the warning is).
If you actually want to FIX the script, the results of find should be read into
an array, since there can be more than one. Every place you use your variable
currently, you'd have to rewrite that to handle an array with potentially
multiple elements.
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