Looks like & saves the day by invoking the command in a subshell and then in that subshell exec replaces the subshell with the xinput command. E.g. you can test

Looks like & saves the day by invoking the command in a subshell and then in that subshell exec replaces the subshell with the xinput command. E.g. you can test it by $ cat ./a.sh #!/bin/sh exec /bin/echo foo & exec /bin/echo bar & which outputs foo and bar. Seems like a special case, just like exec without a command for file descriptor redirection.