So, in my script, I want to start two processes in the background, after this I want to wait for both to complete and I want to get the stdout of the processes in variables.
To run in background, I can use
command &
To get the result in a variable I can run the command within backquotes.
But when I do command & within backquotes, the whole thing becomes blocking.
So, how do I solve my problem?
Commands run in background run in a child process, and there is no way for a child process to modify a parameter (variable) in the parent process. So technically, what you're looking for is impossible.
However, you can store the child's stdout (and, if you wish, stderr) in a file; you'll just have to make sure to give the file a unique name. (See man mktemp, for example.) After you wait for the background process to finish, you can read the temporary file into a parameter, and delete the file.
tmp1=$(mktemp)
tmp2=$(mktemp)
command1 > "$tmp1" &
command2 > "$tmp2" &
wait
OUTPUT1=$( < "$tmp1" ) && rm "$tmp1"
OUTPUT2=$( < "$tmp2" ) && rm "$tmp2"
