If I put a space as the first char in environment variable PARALLEL, it does not obey the "--gnu" option. I haven't tried other options yet.
[felipe(tip)@fred ~]$ unset PARALLEL
[felipe(tip)@fred ~]$ parallel -V
WARNING: YOU ARE USING --tollef. IF THINGS ARE ACTING WEIRD USE --gnu.
GNU parallel 20131222
Copyright (C) 2007,2008,2009,2010,2011,2012,2013 Ole Tange and Free Software Foundation, Inc.
This is free software: you are free to change and redistribute it.
GNU parallel comes with no warranty.
When using GNU Parallel for a publication please cite:
O. Tange (2011): GNU Parallel - The Command-Line Power Tool,
;login: The USENIX Magazine, February 2011:42-47.
[felipe(tip)@fred ~]$ export PARALLEL=' --gnu'
[felipe(tip)@fred ~]$ parallel -V
WARNING: YOU ARE USING --tollef. IF THINGS ARE ACTING WEIRD USE --gnu.
GNU parallel 20131222
Copyright (C) 2007,2008,2009,2010,2011,2012,2013 Ole Tange and Free Software Foundation, Inc.
This is free software: you are free to change and redistribute it.
GNU parallel comes with no warranty.
When using GNU Parallel for a publication please cite:
O. Tange (2011): GNU Parallel - The Command-Line Power Tool,
;login: The USENIX Magazine, February 2011:42-47.
[felipe(tip)@fred ~]$ export PARALLEL='--gnu'
[felipe(tip)@fred ~]$ parallel -V
GNU parallel 20131222
Copyright (C) 2007,2008,2009,2010,2011,2012,2013 Ole Tange and Free Software Foundation, Inc.
This is free software: you are free to change and redistribute it.
GNU parallel comes with no warranty.
When using GNU Parallel for a publication please cite:
O. Tange (2011): GNU Parallel - The Command-Line Power Tool,
;login: The USENIX Magazine, February 2011:42-47.
--
felipe