Send task to background in an "if"

Question

Why is this?

if true; then sleep 3 &; fi
bash: syntax error near unexpected token `;'

I want to run

sleep 3

in the background so that the command ["sleep 3" is just an example] would run in "paralell" style, so it finishes faster. But I'm getting this:

bash: syntax error near unexpected token `;'

error message. Why? Why can't I send a task to the background?

What do you think you're testing with the `if` statement? – glenn jackman Dec 10 '11 at 20:08 — glenn jackman, Dec 10 '11 at 20:08

enzotib · Answer 1 · 2011-12-10T11:52:10.947

14

It is because & is already a statement separator, so you should not put ; after this.

edited Dec 10 '11 at 11:52

answered Dec 10 '11 at 11:33

enzotib

This should be more like the accepted answer than the one from 2011-10-12, 11:34 by @ДМИТРИЙ-МАЛИКОВ. – Golar Ramblar May 31 '21 at 17:15

score 6 · Accepted Answer · answered Dec 10 '11 at 11:34

6

Seems like you don't need to separate commands in that case (& separated them itself).

For example.

$> if true; then (sleep 3; echo ok) &  fi
[1] 14224
$> ok

answered Dec 10 '11 at 11:34

This works but spawns a subshell, i.e. an extra process (which extra memory burden, and variable settings you do inside the `( ... )` will not be visible outside) – Golar Ramblar May 31 '21 at 17:14

score 0 · Answer 3 · answered May 31 '21 at 17:12

0

Try to write it multiline:

if true; then
  sleep 3 &
fi

answered May 31 '21 at 17:12

Golar Ramblar

3 Answers3