从子 shell 中运行的命令中识别 bash 退出代码 - 使用 set -e 时

Question

Obviously $? could be used, but the script contains set -e, which causes an exit as soon as a command fails

A very artifical example:

set -eu -o pipefail
...
# file does_not_exist does not exist
# the following would result in an immediate exit of the script
mv does_not_exist new_file
# as does the following
$(mv does_not_exist new_file)
# but this neat trick doesn't exit the script
declare -r RES=$(mv does_not_exist new_file)
# however I'd also like to get at the exit code of **mv**

Answer 1

You can examine $? in the "or" part of the command:

set -e
ls /does-not-exist || echo $?
echo end

The behaviour is documented in man bash under set :

The shell does not exit if the command that fails is part of the command list immediately following a while or until keyword, part of the test following the if or elif reserved words, part of any command executed in a && or ||list except the command following the final && or ||, any command in a pipeline but the last, or if the command's return value is being inverted with ! .