Zsh Mailing List Archive
Messages sorted by: Reverse Date, Date, Thread, Author

process substitution bug with set -e?

The zshexpn(1) man page of zsh 5.0.2 says:

  There  is  an additional problem with >(process); when this is attached
  to an external command, the parent shell does not wait for  process  to
  finish  and  hence  an immediately following command cannot rely on the
  results being complete.  The problem  and  solution  are  the  same  as
  described  in the section MULTIOS in zshmisc(1).  Hence in a simplified
  version of the example above:

         paste <(cut -f1 file1) <(cut -f3 file2) > >(process)

  (note that no MULTIOS are involved), process will be run asynchronously
  as far as the parent shell is concerned.  The workaround is:

         { paste <(cut -f1 file1) <(cut -f3 file2) } > >(process)

  The  extra  processes here are spawned from the parent shell which will
  wait for their completion.

Now, consider the following script:

#!/usr/bin/env zsh
set -e
{ /bin/cp } 2>>(sleep 1; cat -n)

Due to /bin/cp failure and the "set -e", the parent shell exits
immediately, without waiting for the extra processes:

ypig% ./zsh-procsubst
ypig%      1    /bin/cp: missing file operand
     2  Try '/bin/cp --help' for more information.

(tested under Debian/unstable).

Shouldn't the parent shell wait in this case?

If this is the expected behavior, the man page should be fixed,
and possibly give another workaround in the case of set -e.

Vincent Lefèvre <vincent@xxxxxxxxxx> - Web: <http://www.vinc17.net/>
100% accessible validated (X)HTML - Blog: <http://www.vinc17.net/blog/>
Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)

Messages sorted by: Reverse Date, Date, Thread, Author