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Re: Possible bug with grep/sed/tail?

From: Pádraig Brady
Subject: Re: Possible bug with grep/sed/tail?
Date: Sat, 22 Nov 2008 13:57:55 +0000
User-agent: Thunderbird (X11/20071008)

Jim Meyering wrote:
> Jim Meyering <address@hidden> wrote:
>> Andreas Schwab <address@hidden> wrote:
>>> Paolo Bonzini <address@hidden> writes:
>>>>   alias line-buffer='preload /t/linebuf.so'
>>> If you end the alias expansion with a space then the next word is also
>>> expanded as an alias.
>> Ah, yes.  That was it.  Thanks ;-)
> To summarize, here's what I'm using, now:
> Put the following in your .bashrc or .zshrc file:
>   # Create the .so file with the following.
>   line_buffer_so=$HOME/lib/line-buffer.so
>   line-buffer-init()
>   {
>     echo '__attribute__((constructor))void 
> f(){setvbuf(stdout,NULL,_IOLBF,0);}' \
>       | gcc -s -include stdio.h -x c - -fPIC -shared -o "$line_buffer_so"
>   }
>   alias line-buffer="LD_PRELOAD='$line_buffer_so' "
> As a one-time set-up, you have to run the line-buffer-init function.
> Then you can use it e.g., to watch *interactively* filtered tail -f output.
> For example, watch for warnings in build output like this:
>     make >& log & line-buffer tail -F log | grep warning:

grep --color warning.*

> but that's not quite right, since it hangs forever.
> Add --pid=$! to make tail stop when the parent (make) process dies:
>     make >& log & line-buffer tail -F log --pid=$! | grep warning:

That's a tip and a half.
I'll certainly be using that,
Though I'll probably auto-compile the lib like:

[ ! -x "$line_buffer_so" ] && line-buffer-init()

Of course this solution depends on gcc and LD_PRELOAD etc.

What about adding buffer control to all coretuils filters.
Is that still a desired feature do you think?


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