complex command over ssh [closed] - linux

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Can someone help me to force this script work please
IFLOAD=`ssh root#$REMOTE_HOST 'awk '\''/$IFACE/ {i++; rx[i]=\$2; tx[i]=\$10}; END{print rx[2]-rx[1] " " tx[2]-tx[1]}'\'' <(cat /proc/net/dev; sleep 1; cat /proc/net/dev)'
echo "$IFLOAD"
Now it returns
0 0
But on $2 and $10 columns i have a real data with IFACE rx and tx bytes. Without ssh this script works fine, as i see.
Or maybe you know more easy way to get current measure of interafce load over ssh.

Answer 1

First, let's simplify the awk command a little, before worrying about how to pass it through ssh.
awk_script='
ifc ~ $1 {
i++;
rx[i]=$2;
tx[i]=$10
};
END {
print rx[2]-rx[1] " " tx[2] - tx[1]
}
'
awk -v ifc="$IFACE" "$awk_script" <(cat /proc/dev/net; sleep 1; cat /proc/dev/net)
Passing IFACE as an awk variable lets us enclose the entire awk script in one single-quoted string. As long as we double-quote the expansion, it will work as intended.
Now it should be relatively simple to send via ssh:
IFLOAD=$(ssh root#$REMOTE_HOST "awk -v ifc='$IFACE' '$awk_script' <(cat /proc/dev/net; sleep 1; cat /proc/dev/net)")
Note the entire command line is one double-quoted string. That means $IFACE and $awk_script will be expanded locally. That string, though, uses single quotes around the expansions, so that when the entire thing is sent to the remote shell, each value is seen as a single-quoted string, and won't be incorrectly processed by the remote shell.