RE: Environment variable "PS4" can not be passed to bash script from version 4.2.46(2)

2018-10-23 Thread Chen, Farrah 
Got it, thanks for the info.


Thanks,
Fan



-Original Message-
From: Chet Ramey [mailto:chet.ra...@case.edu] 
Sent: Wednesday, October 24, 2018 4:48 AM
To: Chen, Farrah ; bug-bash@gnu.org
Cc: chet.ra...@case.edu
Subject: Re: Environment variable "PS4" can not be passed to bash script from 
version 4.2.46(2)

On 10/23/18 12:06 PM, Greg Wooledge wrote:
> On Tue, Oct 23, 2018 at 03:20:12PM +, Chen, Farrah wrote:
>> But in Bash script, it cannot work, it keeps its original value:
>> [root@fchen ~]# cat test.sh
>> #!/usr/bin/bash
>> echo $PS4
>> echo $FAN
> 
> This is because you're doing it as root.  Bash strips PS4 from the 
> environment when started as root, as a security precaution.

That change came in in bash-4.3 (patch 48). His vendor probably patched their 
version of bash-4.2 to do the same thing.

--
``The lyf so short, the craft so long to lerne.'' - Chaucer
 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, UTech, CWRUc...@case.eduhttp://tiswww.cwru.edu/~chet/

Re: Environment variable "PS4" can not be passed to bash script from version 4.2.46(2)

2018-10-23 Thread Chet Ramey 
On 10/23/18 12:06 PM, Greg Wooledge wrote:
> On Tue, Oct 23, 2018 at 03:20:12PM +, Chen, Farrah wrote:
>> But in Bash script, it cannot work, it keeps its original value:
>> [root@fchen ~]# cat test.sh
>> #!/usr/bin/bash
>> echo $PS4
>> echo $FAN
> 
> This is because you're doing it as root.  Bash strips PS4 from the
> environment when started as root, as a security precaution.

That change came in in bash-4.3 (patch 48). His vendor probably patched
their version of bash-4.2 to do the same thing.

-- 
``The lyf so short, the craft so long to lerne.'' - Chaucer
 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, UTech, CWRUc...@case.eduhttp://tiswww.cwru.edu/~chet/

Re: Environment variable "PS4" can not be passed to bash script from version 4.2.46(2)

2018-10-23 Thread Greg Wooledge 
On Tue, Oct 23, 2018 at 03:20:12PM +, Chen, Farrah wrote:
> But in Bash script, it cannot work, it keeps its original value:
> [root@fchen ~]# cat test.sh
> #!/usr/bin/bash
> echo $PS4
> echo $FAN

This is because you're doing it as root.  Bash strips PS4 from the
environment when started as root, as a security precaution.

wooledg:~$ PS4='hello' bash -c 'set -x; true'
hellotrue
wooledg:~$ sudo env PS4='hello' bash -c 'set -x; true'
[sudo] password for wooledg: 
+ true

Notice how it works as expected as a regular user, then "fails"
under sudo.

Environment variable "PS4" can not be passed to bash script from version 4.2.46(2)

2018-10-23 Thread Chen, Farrah 
Hello,

I found a strange phenomenon, just as the subject, environment variable "PS4" 
cannot be passed to bash script, but any other variable, even self-defined 
variable can be passed to bash script.
My bash version is "GNU bash, version 4.2.46(2)-release 
(x86_64-redhat-linux-gnu)", I downloaded an old version bash-2.0.tar.gz from 
ftp://ftp.gnu.org/gnu/bash/ and installed, no such issue found, "PS4" works 
well.

I tried to set PS4 in /etc/profile, in /etc/bashrc, and export PS4 in terminal, 
just like below, it is correct in current terminal, but cannot be passed to 
bash script.

export PS4='+[#$LINENO ${FUNCNAME[0]}() $BASH_SOURCE] '
export FAN='Myself'

Then source /etc/profile, /etc/bashrc, I also tried to reboot my machine.
In terminal, it works well:

[root@fchen ~]# echo $PS4
+[#$LINENO ${FUNCNAME[0]}() $BASH_SOURCE]
[root@fchen ~]# echo $FAN
Myself

But in Bash script, it cannot work, it keeps its original value:
[root@fchen ~]# cat test.sh
#!/usr/bin/bash
echo $PS4
echo $FAN

[root@fchen ~]# bash test.sh
bash test.sh
+
Myself

Value of variable "Fan" I set in /etc/profile is correct, but $PS4 keeps its 
original value.
I tried many different variable names, such as "PS3", "PS5", all of them work, 
except "PS4".

I found such problem when we update our os from Red-hat 7.3 to Red-hat 7.4,this 
is a long time ago.
Now, I know that on Red-Hat7.0, bash version 4.2.45(1)-release, no such 
problem; on Red-hat 7.5 bash version 4.2.46(2)-release, on Ubuntu 16.04 bash 
version 4.3.48(1)-release, both have this issue.
I assume this issue occurs after version 4.2.46.
PS4 is used by "set -x" to prefix tracing output, it is very useful for our 
work, but it doesn't work now, I'm confused.

Thanks a lot.


Thanks,
Fan