How do I make find fail if -exec fails?
This is a limitation of find. The POSIX standard specifies that the return status of find is 0 unless an error occurred while traversing the directories; the return status of executed commands doesn't enter into it.

You can make commands write their status to a file or to a descriptor:

find_status_file=$(mktemp findstatus)
: &gt;"$find_status_file"
find … -exec sh -c 'trap "echo \$?" EXIT; invalid_command "$0"' {} \;
if [ -s "$find_status_file" ]; then
  echo 1&gt;&amp;2 "An error occurred"
fi
rm -f "$find_status_file"


Another method, as you discovered, is to use xargs. The xargs commands always processes all files, but returns the status 1 if any of the commands returns a nonzero status.

find … -print0 | xargs -0 -n1 invalid_command


Yet another method is to eschew find and use recursive globbing in the shell instead: **/ means any depth of subdirectories. This requires version 4 or above of bash; macOS is stuck at version 3.x so you'd have to install it from a port collection. Use set -e to halt the script on the first command returning a nonzero status.

shopt -s globstar
set -e
for x in **/*.xml; do invalid_command "$x"; done


Beware that in bash 4.0 through 4.2, this works but traverses symbolic links to directories, which is usually not desirable.

If you use zsh instead of bash, recursive globbing works out of the box with no gotchas. Zsh is available by default on OSX/macOS. In zsh, you can just write

set -e
for x in **/*.xml; do invalid_command "$x"; done