How can I run a command at the background without ampersand (&)?

Question

How can I run a command at the background in Bash without ampersand (&) at the end of a command?

Update: I want to do it so I can do while inotifywait -e modify app.py; do killall -9 python; python app.py &; done, but that isn't possible because of the syntax.

Please [edit] and explain what you are trying to do. The `&` _is_ the way to run a command in the background. Why don't you want to use it? Do you want to send an already launched command to the background? — terdon, Oct 25 '15 at 16:41
@Jos my `&` key isn't broken and @terdon I updated the question — wb9688, Oct 26 '15 at 06:17

score 6 · Accepted Answer · edited Oct 26 '15 at 09:06

Use coproc python app.py

From man bash

Coprocesses

A coprocess is a shell command preceded by the coproc reserved word. A coprocess is executed asynchronously in a subshell, as if the command had been terminated with the & control operator, with a two-way pipe estab‐ lished between the executing shell and the coprocess.

The format for a coprocess is:

coproc [NAME] command [redirections]

score 2 · Answer 2 · answered Oct 26 '15 at 09:53

Your syntax is slightly off:

while inotifywait -e modify app.py; do killall -9 python; python app.py &; done

It should be:

while inotifywait -e modify app.py; do killall -9 python; python app.py & done

Unlike C-like languages, you cannot have an empty statement before ; or &.

How can I run a command at the background without ampersand (&)?

2 Answers2