On Mon, Jul 30, 2012 at 02:17:15PM -0700, Andrew Resch wrote: > I am attempting to use exec and tee to have my scripts > stdout/stderr appended to a log file like such: exec > >(tee -a $LOG) > 2>&1 > These scripts will often call other scripts with a similar > exec statement, often writing to a separate log file. On my GNU/Linux > systems, > these scripts will run just fine without any issue, but on > HP-UX they seem to hang or not display any output.
The major difference here is that bash on HP-UX implements process substitutions (the <() syntax) with a named pipe, whereas on Linux it uses a /dev/fd/* file. > $ cat test_exec1.sh > #!/bin/bash > > LOG="test_exec.log" > exec > >(/usr/bin/tee -a $LOG) 2>&1 > > echo "i am exec1.." > > ./test_exec2.sh > > echo "i am done in exec1.." > $ while true; do ./test_exec1.sh; done You are opening a slew of named pipes and background jobs in rapid succession, and not waiting for the jobs to finish. (It might still be considered a bug... I'm just pointing out the practical aspects.) I would bet that putting a "sleep 1" in the loop would make the problem stop happening, as horrible a hack as that may be. I discuss this a bit on <http://mywiki.wooledge.org/BashFAQ/106>. The only way to ensure clean operation is to avoid the <() syntax altogether and use your own explicit named pipe and background job. Then you can close the pipe and wait for the background job to terminate before exiting.
