Recently while crafting a Vagrantfile I came across the need of checking if I had already added a route to my host when reload the vagrant box.

Listing routes
netstat -nr  
  • -r shows the routing table
  • -n shows the network addresses as number
Matching the pattern
grep -co '172.17 *'  
  • -c writes the number of matches to stdout
  • -o prints only the matching part of the line

Putting both commands together

if [ $(netstat -nr | grep -co '172.17 *') = 0 ]; then  
        echo 'Adding gateway route for docker0 network'
        sudo route -n add " + $vb_ip_address + "