[Help-bash] backgrounding a process sends it into a tailspin

[Cook, Rich]

Hello, 
I have built and installed gnuplot and wrapped it in a bash script.  The script 
simply makes a usage entry in a database, calls gnuplot, then notes that it 
exits.  I'm including the script below.  

When the user runs this script and puts it into the background, gnuplot 
immediately starts taking up 100% of a CPU, spinning in readline.  This only 
happens when gnuplot is wrapped in this way, not when it's called directly.  I 
would like to avoid this behavior, obviously, but I would also like to continue 
using a wrapper script.  What is it about being called from a script that is 
causing this odd behavior on gnuplot's part?  

I know this sounds like a gnuplot question, but I also think it requires expert 
understanding of job control to decipher.  I'm hoping someone on this list has 
such expertise. 

Thanks.  

Here's a stack trace from a debugger of gnuplot when it's hammering our CPU:  
Stack Trace
    tcsetattr,           FP=7fffffffd060
    rl_tty_unset_default_bindings, FP=7fffffffd080
    rl_deprep_terminal,  FP=7fffffffd090
    rl_cleanup_after_signal, FP=7fffffffd0a0
    rl_reset_after_signal, FP=7fffffffd140
    rl_read_key,         FP=7fffffffd160
    readline_internal_char, FP=7fffffffd180
    readline,            FP=7fffffffd190
C    read_line,           FP=7fffffffd1e0
C    com_line,            FP=7fffffffd1f0
C    main,                FP=7fffffffd3e0
    __libc_start_main,   FP=7fffffffd4a0
    _start,              FP=7fffffffd4b0


Here's the wrapper script:  

#!/usr/bin/env bash

IMG_TRACK=${IMG_TRACK:-/usr/local/tools/imgtrack-1.0/bin/imgtrack}
if [ -f $IMG_TRACK ]; then 
   $IMG_TRACK BEGIN gnuplot-4.4.3 $0 "$@"
fi
/usr/local/tools/gnuplot-4.4.3/bin/gnuplot.real "$@"
_value=$?
if [ -f $IMG_TRACK ]; then 
   $IMG_TRACK END gnuplot-4.4.3 $0 "$@"
fi
exit $_value

-- 
✐Richard Cook   
✇ Lawrence Livermore National Laboratory
Bldg-453 Rm-4024, Mail Stop L-557        
7000 East Avenue,  Livermore, CA, 94550, USA
☎ (office) (925) 423-9605    
☎ (fax) (925) 423-6961
---
Information Management & Graphics Grp., Services & Development Div., Integrated 
Computing & Communications Dept.
(opinions expressed herein are mine and not those of LLNL)