Echo within bash subshell

Question

How do I call echo from within a bash subshell? This is behavior I want:

# w=5
# echo $w > /tmp/x
# cat /tmp/x
5

But:

# cmd="echo $w > /tmp/x"
# $cmd
5 > /tmp/x

And:

# $( $cmd )
bash: 5: command not found

Answer 1

Your problem is not echo .

Your problem is the redirection. You can't put redirection inside a string.

That's why you get echo outputting 5 > /tmp/x in your first attempt.

The problem with your second attempt is that you "lose" the echo by the time the $() tries to run the output (because as your first attempt shows your output from $cmd is 5 > /tmp/x which isn't a valid command.

That said this is Bash FAQ 050 so stop trying to put commands in variables. It doesn't work.