RE: Replacement strings

[Cook, Malcolm]

Ole,

After hitting 'send', two thoughts

1) you could also profitably and easily(?) extend parallel to simply allow 
specifying the SHELL to be something other.  Like Perl!

2) my example of removing multiple extensions should NOT have had a column for 
'current syntax' for, of course, there is none.   Yet at least.

Malcolm

 >-----Original Message-----
 >From: Cook, Malcolm
 >Sent: Wednesday, June 25, 2014 12:18 PM
 >To: 'Ole Tange'; 'parallel@gnu.org'
 >Subject: RE: Replacement strings
 >
 >Ole!
 >
 >I would like to see something like this in parallel.
 >
 >I don't think fex provides a good model for the syntax.
 >
 >Given that your implementation is in Perl, you might consider extending the 
 >syntax to allow
 >      any Perl expression can appear between the braces
 >      the expression is evaluated in the context where $_ is bound to the 
 > (chomped) current line of input.
 >      the value of the bracketed expression is the value of $_ after 
 > evaluating the expression.
 >
 >Then you could write, for example:
 >
 >example                       current syntax          meaning / note
 >{$_}                          {}                      the current line
 >{s/\.[^.]+$//}                        {.}                     the current 
 >line after trimming an extension (but, dangerous, as written would
 >trim from first '.' even if part of dirname)
 >{qx|basename $_|}             {/}                     basename - directory 
 >removed - uses perl qx operator to call out to system
 >{qx|dirname $_|}              {/}                     directory name
 >
 >
 >Removal of multiple extensions is now a matter or writing the regex:
 >
 >{s/(\.[^.]+$){2}//}                   {.}                     the current 
 >line after trimming exactly two extensions
 >{s/(\.[^.]+$){,2}//}                  {.}                     the current 
 >line after trimming up to two extensions
 >
 >Other possibilities immediately come to mind
 >
 >find . -name '*.tif' | parallel mv {} '{s/(\d+)/sprintf("%07s",$1)/}'   # 
 >rename all tif files so numeric stem is zero padded in a field of 7
 >zeros
 >find images -type d | parallel -j1  mkdir -p {/^images/cropped.images/}       
 >        # create 'cropped.images' directory structure parallel
 >to 'images' nb -j1 is required to avoid contention
 >find images -name '*.tif' | parallel  crop {}   {/^images/cropped.images/}    
 >        # `crop` all tifs in thisdir into a parallel directory
 >structure
 >
 >Also, handling of --header options  such as your examples with $gender and 
 >$size, could also allow recodings, such as:
 >
 >{switch($gender) { switch case "m" "male" case "f" "female"
 >
 >I think this might sit VERY NICELY with your implementation, and provide LOTS 
 >of new USEFUL and SUCCINT idiomatic uses of parallel.
 >
 >On the topic, both bash and gnu make provide syntax for parameter expansion 
 >which might fruitfully be co-opted to your purpose.
 >But I like using the perl model.
 >
 >Cheers,
 >
 >Malcolm
 >
 > >-----Original Message-----
 > >From: parallel-bounces+mec=stowers.org@gnu.org 
 > >[mailto:parallel-bounces+mec=stowers.org@gnu.org] On Behalf Of Ole Tange
 > >Sent: Tuesday, June 03, 2014 4:56 PM
 > >To: parallel@gnu.org
 > >Subject: Replacement strings
 > >
 > >Currently GNU Parallel has 6 replacement strings:
 > >
 > >{} = A/B/C.D.E
 > >{.} = A/B/C.D
 > >{#} = Job number
 > >{%} = Job slot
 > >{//} = A/B
 > >{/} = C.D.E
 > >{/.} = C.D
 > >
 > >(Plus the numbered {1} and {-1}).
 > >
 > >But there has been a demand for removing two extensions and a
 > >replacement string for the removed extension. If these should be
 > >implemented, I would like to have a more general syntax. It could be
 > >something like:
 > >
 > >{+.} = E
 > >{+/} = A/B
 > >{..} = A/B/C
 > >{+..} = D.E
 > >
 > >{} = {.}.{+.} = {+/}/{/} = {+/}/{/.}.{+.} = {..}.{+..}
 > >
 > >The idea is here that '+' matches the opposite of the non-+ version
 > >(except for the . or / separating). {//} would be the only redundant
 > >string (in the new syntax that is {+/}).
 > >
 > >If it is easy to implement then {...} {/..} {/...} and the +-versions
 > >should work, too.
 > >
 > >There would still no replacement string for 'A', 'B' or 'D'.
 > >
 > >Better ideas for syntax? Is there any good existing syntax for
 > >replacements that would make sense? E.g. FEX
 > >http://www.semicomplete.com/projects/fex/
 > >
 > >
 > >/Ole