GNU Parallel 20140711alpha released

[Ole Tange]

GNU Parallel 20140711alpha has been released. It is available for
download at: http://alpha.gnu.org/gnu/parallel/parallel-20140711.tar.bz2

Thanks to Malcolm Cook this alpha release features a major change: Use
a general perl expression as a replacement string. I have a feeling
this will prove to be super cool.

  parallel echo '{= s:\.[^/.]+$::;s:\.[^/.]+$:: =}' ::: dir/file.ext1.ext2

You can also define your own replacement string using --rpl. This way
remove two file extensions can be done:

  parallel --rpl '{..} s:\.[^/.]+$::;s:\.[^/.]+$::' echo {..} :::
dir/file.ext1.ext2

If you choose your replacement string to start with { it works
automatically for positional replacement:

  parallel -N3 --rpl '{..} s:\.[^/.]+$::;s:\.[^/.]+$::' echo {2..} :::
foo dir/file.ext1.ext2 bar

This alpha release has known bugs (e.g. {%} does not work with --pipe)
but should be usable for most situations.

The changes to get the basic perl replacement string to work was
remarkably easy, but getting all the corner cases to work has be quite
a task. So the code changes have been quite extensive and have been in
the core of the code making it likely that some functionality is
broken.

Let us see if you can find bugs, that are not found by my testsuite
yet. I am especially interested in things that make it crash or go
into an infinite loop.

Excerpt from man page below.


/Ole

{=perl expression=}
 Replace with calculated perl expression. $_ will contain the same as
{}. After evaluating perl expression $_ will be used as the value. It
is recommended to only change $_ but you have full access to all of
GNU parallel's internal functions and data structures.

 See also: --rpl --parens

--parens parensstring (alpha testing)
 Use to define start and end parenthesis for {= perlexpr =}. The left
and the right parenthesis can be multiple characters and are assumed
to be the same length. The default is {==} giving {= as the start
parenthesis and =} as the end parenthesis.

 Another useful setting is ,,,, which would make both parenthesis ,,.

 See also: --rpl {= perlexpr =}

--rpl 'tag perl expression' (alpha testing)
 Use tag as a replacement string for perl expression. This makes it
possible to define your own replacement strings. GNU parallel's 7
replacement strings are implemented as:

  --rpl '{} '
  --rpl '{#} $_=$job->seq()'
  --rpl '{%} $_=$job->slot()'
  --rpl '{/} s:.*/::'
  --rpl '{//} $Global::use{"File::Basename"} ||= eval "use
File::Basename; 1;"; $_ = dirname($_);'
  --rpl '{/.} s:.*/::; s:\.[^/.]+$::;'
  --rpl '{.} s:\.[^/.]+$::'

 If the user defined replacement string starts with '{' it can also be
used as a positional replacement string (like {2.}).

 It is recommended to only change $_ but you have full access to all
of GNU parallel's internal functions and data structures.

 See also: {= perlexpr =} --parens