it, soRE: set -a leads to truncated output from ps

[Alain BROSSARD]

Hi,

   It still doesn’t explain why this is happening.

   If you simply do :

export COLUMNS=60
ps ax | grep java

    The output isn’t truncated.  Remember that PS’s output goes through a pipe 
so the terminal width shouldn’t matter. Without “-a”, we always get the full 
output.
It is critical that application’s behaviour do not get impacted by the shell 
used to call them.  That said, further testing shows a different behavior
# bash
host:/$ echo $COLUMNS
102
host:/$ export COLUMNS
host:/$ ps ax | grep java | head -1
2051669 ?        Sl     0:07 /usr/lib/jvm/java-17-openjdk-amd64/bin/java -Xms2g 
-Xmx2g -server -XX:+Us
host:/$ export COLUMNS=40
host:/$ ps ax | grep java | head -1

     No output whatsoever from the above pipe. So maybe, maybe, a combination 
of two bugs,


  1.  Bash with -a , under some conditions, exports to the environment the 
variable COLUMNS which it shouldn’t
  2.  When  COLUMNS is defined, ps behaves strangely

      A diff before and after of the environment now gives me a difference :
host[195] diff /tmp/env-before /tmp/env-after
1a2
> COLUMNS=102
36a38
> LINES=35

     The strange thing is that I had tested the environment and hadn’t detected 
a change before. I must have made a mistake on that one.


What do you think ?

Regards,
Alain


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From: Oğuz <oguzismailuysal@gmail.com>
Sent: Thursday, June 13, 2024 4:25 PM
To: Alain BROSSARD <abrossard@reyl.com>
Cc: bug-bash@gnu.org
Subject: Re: set -a leads to truncated output from ps

On Thursday, June 13, 2024, Alain BROSSARD via Bug reports for the GNU Bourne 
Again SHell <bug-bash@ gnu. org> wrote: # however, the second one has truncated 
output to the terminal width Looks like `set -a' exports COLUMNS for some 
reason,
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On Thursday, June 13, 2024, Alain BROSSARD via Bug reports for the GNU Bourne 
Again SHell <bug-bash@gnu.org<mailto:bug-bash@gnu.org>> wrote:
       # however, the second one has truncated output to the terminal width

Looks like `set -a' exports COLUMNS for some reason, this must be a bug

$ set -a
$ env | grep COLUMNS
$ env | grep COLUMNS
COLUMNS=64

You should call ps with the option -w if you want wide output though. On some 
implementations you can disable truncation completely by specifying it twice 
like `ps axww'.


--
Oğuz