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I am attempting to write a bash loop that passes a bash string into netcat. The command that I execute is:

nc -nv [ipaddress] [port] << EOF
10000
EOF

I am writing a bash loop to perform this and I've tried a number of options. Here's the basic one I've tried that doesn't seem to work:

#!/bin/bash
# declare number
COUNTER=0
END=$(bc <<< -2^10)
while [ $COUNTER -gt $END ]; do
        nc -nv [IPADDRESS] [PORT] << $COUNTER
        let COUNTER=COUNTER-1
done
share|improve this question
    
The << operator takes a string and then reads everything until it finds that string again. You need <<EOF\n$COUNTER\nEOF. – grochmal Jun 12 '16 at 0:10
    
Since you appear to want to send only a single value, why not use a here string <<< "$COUNTER" rather than trying to use a here document? – steeldriver Jun 12 '16 at 0:16
up vote 1 down vote

Thanks to grochmal and steeldriver for the ideas. The answer was to use <<< 

#!/bin/bash
# declare number
COUNTER=0
END=$(bc <<< -2^10)
while [ $COUNTER -gt $END ]; do
    nc -nv [IPADDRESS] [PORT] <<< $COUNTER
    let COUNTER=COUNTER-1
done

If you want more information about here strings it can be found at: http://www.tldp.org/LDP/abs/html/x17837.html

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