[PATCH] Add new program: psub

[Bo Borgerson]

Hi,

This program uses the temporary fifo management system that I built
for zargs to provide generic process substitution for arguments to a
sub-command.

This program has some advantages over the process substitution built
into some shells (bash, zsh, ksh, ???):

1. It doesn't rely on having a shell that supports built-in process
substitution.
2. By using descriptively named temporary fifos it allows programs
that include filenames in output or diagnostic messages to provide
more useful information than with '/dev/fd/*' inputs.
3. It supports `--files0-from=F' style argument passing, as well.

Examples:

Where in bash you might do:

$ uniq bigfile | tee >(wc -l > bigfile-uniq.count) | gzip -c > bigfile-uniq.gz

With psub you would do:

$ uniq bigfile | psub tee ">wc -l > bigfile-uniq.count" | gzip -c >
bigfile-uniq.gz


And where in bash you might do:

$ wc -l <(ls a) <(ls b)
      2 /dev/fd/63
      1 /dev/fd/62
      3 total

With psub you could do:

$ psub wc -l "<ls a" "<ls b"
      2 /tmp/psub25j3Al/ls a
      1 /tmp/psub25j3Al/ls b
      3 total

Or even:

$ find * -maxdepth 0 -type d | sed "s/^/<ls /" | tr '\n' '\0' | psub
wc -l --files0-from=-
      2 /tmp/psubSZT8xC/ls a
      5 /tmp/psubSZT8xC/ls autom4te.cache
      1 /tmp/psubSZT8xC/ls b
     20 /tmp/psubSZT8xC/ls build-aux
     13 /tmp/psubSZT8xC/ls doc
      3 /tmp/psubSZT8xC/ls gl
     19 /tmp/psubSZT8xC/ls gnulib
    269 /tmp/psubSZT8xC/ls gnulib-tests
    648 /tmp/psubSZT8xC/ls lib
    299 /tmp/psubSZT8xC/ls m4
    203 /tmp/psubSZT8xC/ls man
      3 /tmp/psubSZT8xC/ls old
    121 /tmp/psubSZT8xC/ls po
    345 /tmp/psubSZT8xC/ls src
     49 /tmp/psubSZT8xC/ls tests
   2000 total

The attached version doesn't include any `doc/' or `tests/' yet, but
should be functional enough to give a sense of usage.  If this looks
like something that might be a useful addition to coreutils I'll be
happy to write some documentation and tests and resubmit.

Also available for fetch at:

$ git fetch git://repo.or.cz/coreutils/bo.git psub:psub

Thanks,

Bo

coreutils-psub.diff
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