I'm trying to redirect a command's output in a file only if the command has been successful because I don't want it to erase its content when it fails.
(command is reading the file as input)
I'm currently using
cat <<< $( <command> ) > file;
Which erases the file if it fails.
It's possible to do what I want by storing the output in a temp file like that:
<command> > temp_file && cat temp_file > file
But it looks kinda messy to me, I want avoid manually creating temp files (I know <<< redirection is creating a temp file)
I finally came up with this trick
cat <<< $( <command> || cat file) > file;
Which will not change the contents of the file... but which is even more messy I guess.
Perhaps capture the output into a variable, and echo the variable into the file if the exit status is zero:
output=$(command) && echo "$output" > file
Testing
$ out=$(bash -c 'echo good output') && echo "$out" > file
$ cat file
good output
$ out=$(bash -c 'echo bad output; exit 1') && echo "$out" > file
$ cat file
good output