Re: [Help-bash] procps output truncated due to bash setting $COLUMNS

[Pierre Gaston]

On Tue, Jan 1, 2013 at 8:26 AM,  <address@hidden> wrote:
> Configuration Information [Automatically generated, do not change]:
> Machine: x86_64
> OS: linux-gnu
> Compiler: gcc -I/home/abuild/rpmbuild/BUILD/bash-4.2 
> -L/home/abuild/rpmbuild/BUILD/bash-4.2/../readline-6.2
> Compilation CFLAGS:  -DPROGRAM='bash' -DCONF_HOSTTYPE='x86_64' 
> -DCONF_OSTYPE='linux-gnu' -DCONF_MACHTYPE='x86_64-suse-linux-gnu' 
> -DCONF_VENDOR='suse' -DLOCALEDIR='/usr/share/locale' -DPACKAGE='bash' -DSHELL 
> -DHAVE_CONFIG_H   -I.  -I. -I./include -I./lib   -fmessage-length=0 -O2 -Wall 
> -D_FORTIFY_SOURCE=2 -fstack-protector -funwind-tables 
> -fasynchronous-unwind-tables -g  -D_GNU_SOURCE -DRECYCLES_PIDS -Wall -g 
> -std=gnu89 -Wuninitialized -Wextra -Wno-unprototyped-calls -Wno-switch-enum 
> -Wno-unused-variable -Wno-unused-parameter -ftree-loop-linear -pipe 
> -fprofile-use
> uname output: Linux ares07 3.4.18-jng6-default #1 SMP Wed Nov 14 17:04:47 UTC 
> 2012 (21e90c1) x86_64 x86_64 x86_64 GNU/Linux
> Machine Type: x86_64-suse-linux-gnu
>
> Bash Version: 4.2
> Patch Level: 24
> Release Status: release
>
> Description:
>         procps-3.3.3 and later versions truncate their output at $COLUMN
>         columns, for example when executing `ps | less -S`.
>         The logic procps uses is, in this order, quoted from the source:
>
>         // 1. Defaults are implementation-specific. (ioctl,termcap,guess)
>         // 2. COLUMNS and LINES override the defaults. (standards compliance)
>         // 3. Command line options override everything else.
>         // 4. Actual output may be more if the above is too narrow.
>
>         This sounds reasonable. What makes it awkward is that bash *always*
>         has $COLUMNS set. That looks like an undesired feature to me.
>
>         tcsh for example does not set $COLUMNS on its own.
>
>         The question here is: should bash not set $COLUMNS, or should ps
>         ignore $COLUMNS if not outputting to a tty, or something else?
>
> Repeat-By:
>         ps | less
>
>         Observe how one does not get more than $COLUMNS worth of output,
>         even though ps's stdout is not a tty.
>
> Fix:
>         My proposed "fix" is to turn off automatic setting of $COLUMNS -
>         or at least to not export it if it was automatically set.
>

Bash sets COLUMNS when interactive, but it does not export it so it
should not interfere with other tools unless it is exported in one of
your startup files.