On 8/6/20 6:05 AM, Jason A. Donenfeld wrote: > Hi, > > It may be a surprise to some that this code here winds up printing > "done", always: > > $ cat a.bash > set -e -o pipefail > while read -r line; do > echo "$line" > done < <(echo 1; sleep 1; echo 2; sleep 1; false; exit 1) > sleep 1 > echo done > > $ bash a.bash > 1 > 2 > done > > The reason for this is that process substitution right now does not > propagate errors. It's sort of possible to almost make this better > with `|| kill $$` or some variant, and trap handlers, but that's very > clunky and fraught with its own problems. > > Therefore, I propose a `set -o substfail` option for the upcoming bash > 5.1, which would cause process substitution to propagate its errors > upwards, even if done asynchronously. > > Chet - thoughts?
I don't like it, for two reasons: 1. Process substitution is a word expansion, and, with one exception, word expansions don't contribute to a command's exit status and consequently the behavior of errexit, and this proposal isn't compelling enough to change that even with a new option; and 2. Process substitution is asynchronous. I can't think of how spontaneously changing $? (and possibly exiting) at some random point in a script when the shell reaps a process substitution will make scripts more reliable. -- ``The lyf so short, the craft so long to lerne.'' - Chaucer ``Ars longa, vita brevis'' - Hippocrates Chet Ramey, UTech, CWRU c...@case.edu http://tiswww.cwru.edu/~chet/