问题
When one of my programs returns with a non-zero exit code, I want to avoid redirecting its output. Is this possible, and, if so, how do I do this?
My failed attempt:
echo foo > file
false | cat > file
this results in file being empty. The behaviour I want is to only adjust file when the program succeeds.
I also wonder whether it is possible do only update a file if the output is non-empty, without using multiple files.
回答1:
You can use it like this:
out=$(some_command) && echo "$out" > outfile
echo "$out" > outfile will execute only when some_command succeeds.
回答2:
if avoiding empty file creation and deletion is not essential, maybe it is a good replacement
false > file || rm -f file
来源：https://stackoverflow.com/questions/31424456/how-to-redirect-output-of-a-program-only-if-it-succeeded