Re: Possible bug with grep/sed/tail?

[Jim Meyering]

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:

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: