I'd like to be able to redirect a command, or not, by setting a variable - this is my attempt that doesn't work, does anyone know why/how I can get it to?
# REDIRECT is not set - this works fine
$ echo hi ${REDIRECT}
hi
# If I set this, I want to redirect to tmp...
$ REDIRECT="> /tmp/tmp"
# ...but this passes it as an argument to echo
$ echo hi ${REDIRECT}
hi > /tmp/tmp
I can't just set REDIRECT to the filename as sometimes I don't want to redirect at all, and later I'll possibly want to pipe (e.g. REDIRECT="| tee -a ...").
Anyone know how I can get bash to interpret the values as redirects, not arguments?
It sounds like an XY problem. Rather than trying to redirect based on a variable, just do the redirect when you otherwise would have set the variable. In other words, instead of:
# BROKEN
if want_to_redirect; then
REDIRECT="> /tmp/tmp"
fi
echo hi $REDIRECT # DOES NOT WORK
You can do:
exec 3>&1
if want_to_redirect
exec > /tmp/tmp
fi
echo hi
# If you want output of further commands to go back
# to the original output stream:
exec >&3
In the above want_to_redirect is some command that perhaps checks the environment or in some way decides whether or not you want to redirect; it's not really important what it is. The point is: redirect the output of the shell, since all the commands that the shell executes will inherit its output streams.