Question

I’m having issues implementing this awk statement that I need for my script:

rsh fooDNS '
    ...

    BROADCAST_IP_ADDRESS=$(/usr/sbin/ifconfig $IF_NAME | grep broadcast |  awk '{print \$6}')
    ...
'

The issue here is that the statement above is contained within an rsh command surrounded by single quotations. Consequently, bash cannot interpret the single quotations around {print $6}, which is giving me a lot of problems. So far, I haven’t been able to determine how to get around this issue.

Answer 1

You can’t nest single quotes, but you can end the single quoted string, include an escaped single quote, and then re-enter the quotes. Try this:

rsh fooDNS '
    ...

    BROADCAST_IP_ADDRESS=$(/usr/sbin/ifconfig $IF_NAME | grep broadcast |  awk '\''{print $6}'\'')
    ...
'

Nonetheless, this kind of quoting madness gets ugly very quickly. If at all possible, I recommend using scp/rcp/ftp to copy a normal bash script over to the remote and then run that. Failing that, I think you can use a trick like this if you don’t need to feed anything to the script’s stdin:

cat script_file | rsh fooDNS bash

(Use rsh fooDNS /bin/sh if your script is plain-sh-compatible and the remote side doesn’t have bash, of course.)

As yet another alternative, if your snippet is short you can use here docs:

rsh fooDNS sh <<'EOF'
    ...
    BROADCAST_IP_ADDRESS=$(/usr/sbin/ifconfig $IF_NAME | grep broadcast |  awk '{print $6}')
    ...
EOF