RE: option for performing dry run

[Cook, Malcolm]

Ole,

The value to me of being able to see the command that would execute without 
executing is when I am debugging the creation of a parallel job.

When they get at all complicated, such as using your clever means for 
interpolating filenames into the command strings, and issues regarding 
whitespace and escape characters in commands, it is good to see the commands 
that are going to be executed without running them.

--dry-run gives me this ability as coded, so, nothing really need change.  It 
just got me musing.... I thought it might be of interest.... but really there 
is nothing to do for me but incorporate --dry-run in next release.

I am interested in the effect of --dry-run as coded on --trc.  Will the --trc 
actually happen or not?

Thx

Malcolm Cook
Stowers Institute for Medical Research -  Bioinformatics
Kansas City, Missouri  USA
 
 

> -----Original Message-----
> From: ole.tange@gmail.com [mailto:ole.tange@gmail.com] On 
> Behalf Of Ole Tange
> Sent: Wednesday, December 15, 2010 9:18 AM
> To: Cook, Malcolm
> Cc: parallel@gnu.org
> Subject: Re: option for performing dry run
> 
> On Wed, Dec 15, 2010 at 3:20 PM, Cook, Malcolm 
> <MEC@stowers.org> wrote:
> > As implemented, it seems to do what I've asked.  Thanks!
> 
> Good.
> 
> > But....thinking about it a little more.... hmmmm....
> >
> > You have many command line options.  Appreciating them all 
> without having had to use them all is a small challenge....
> 
> No one uses them all. Not even me. But people use different 
> subsets of them.
> 
> > I note that parallel by default is --silent and has option 
> to be --verbose, which shows the command before executing.
> >
> > GNU make, onthe other hand, by default is --verbose (it 
> prints each command immediately before execution) and has 
> option to be --silent which squelches this trace.
> >
> > Assuming this is not going to change....
> 
> In practice it is rare that I need -v. More often I want to 
> be able to process the output. A simple example is the 
> parallel grep from the
> manpage:
> 
>        find . -type f | parallel -k -j150% -n 1000 -m grep -H 
> -n STRING {}
> 
> Here I can simply treat the output as I would the output from grep.
> 
> > I think you might provide a flag to '--forgo' execution of 
> the command, the 'transfer' and/or the 'cleanup'.  Then allow 
> -v to control what gets echoed to STDOUT.
> >
> > This new flag would also control whether jobs are submitted 
> to remote hosts.  Also, if set, files would not be 
> transferred but (if --verbose) the commands to effect the 
> transfer ('rsync' etc) would be printed.
> >
> > You _might_ call the flag --forgo (-f) with default value 
> of 'all' but option to set it to one or more of 'transfer' 
> 'return' 'cleanup'.
> >
> > --dry-run is then equivilent to '--verbose --forgo all'
> 
> With your description it is not clear to me what --forgo should do.
> 
> If you do not what a job sent to a remote machine, simply put only ':'
> in the -S or leave -S out.
> 
> 
> /Ole
>