Invalid preceding regex

Question

I receive error:

awk: bad regex '{|:|}': Invalid preceding regular expression {"arguments":{},"result":"success"} {"port":37482}

Which I believe is related to this line:

PORT=$(echo $json | awk 'BEGIN{r=1;FS="{|:|}"} /port/{r=0; print $3} END{exit r}')
#echo $PORT

Does anyone know what it means and how I can fix it? I am new to scripting but as I understand it the expression |:| is incorrect. $json is a file I am pulling from my VPN with port information for forwarding.

My input:

#!/usr/bin/env bash
#
# Enable port forwarding when using Private Internet Access
#
# Usage:
#  ./port_forwarding.sh
TRANSUSER=xxx
TRANSPASS=xxxx
TRANSHOST=localhost
error( )
{
  echo "$@" 1>&2
  exit 1
}
error_and_usage( )
{
  echo "$@" 1>&2
  usage_and_exit 1
}
usage( )
{
  echo "Usage: `dirname $0`/$PROGRAM"
}
usage_and_exit( )
{
  usage
  exit $1
}
version( )
{
  echo "$PROGRAM version $VERSION"
}

port_forward_assignment( )
{
  client_id_file="/etc/openvpn/pia_client_id"
  if [ ! -f "$client_id_file" ]; then
    if hash shasum 2>/dev/null; then
      head -n 100 /dev/urandom | shasum -a 256 | tr -d " -" > "$client_id_file"
    elif hash sha256sum 2>/dev/null; then
      head -n 100 /dev/urandom | sha256sum | tr -d " -" > "$client_id_file"
    else
      echo "Please install shasum or sha256sum, and make sure it is visible in your \$PATH"
      exit 1
    fi
  fi
  client_id=`cat "$client_id_file"`
  json=`curl "http://209.222.18.222:2000/?client_id=$client_id" 2>/dev/null`
  if [ "$json" == "" ]; then
    json='Port forwarding is already activated on this connection, has expired, or you are not connected to a PIA region that supports port forwarding'
  fi
  echo $json
}
#trim VPN forwarded port from JSON
PORT=$(echo $json | awk 'BEGIN{r=1;FS="{|:|}"} /port/{r=0; print $3} END{exit r}')
#echo $PORT
#change transmission port on the fly
CURLOUT=$(curl -u $TRANSUSER:$TRANSPASS ${TRANSHOST}:9091/transmission/rpc 2>/dev/null)
REGEX='X-Transmission-Session-Id\: (\w*)'

if [[ $CURLOUT =~ $REGEX ]]; then
    SESSIONID=${BASH_REMATCH[1]}
else
    exit 1
fi
DATA='{"method": "session-set", "arguments": { "peer-port" :'$port' } }'

curl -u $TRANSUSER:$TRANSPASS http://${TRANSHOST}:9091/transmission/rpc -d "$DATA" -H "X-Transmission-Session-Id: $SESSIONID"

EXITCODE=0
PROGRAM=`basename $0`
VERSION=2.1
while test $# -gt 0
do
  case $1 in
  --usage | --help | -h )
    usage_and_exit 0
    ;;
  --version | -v )
    version
    exit 0
    ;;
  *)
    error_and_usage "Unrecognized option: $1"
    ;;
  esac
  shift
done
port_forward_assignment
exit 0

The script is taken from: https://www.privateinternetaccess.com/forum/discussion/23431/new-pia-port-forwarding-api/p3?

It is designed to make a request to their API for a port number and then to forward that port received into transmission daemon.

Answer 1

If you are asking "How can I get the port number from this input data?", with the following data:

{"arguments":{},"result":"success"} {"port":37482}

Then I'd advise you look at jq:

$ echo '{"arguments":{},"result":"success"} {"port":37482}' | jq -s '.[1].port'
37482

---

jq -s will "slurp" the input into an array, this is necessary as you are providing two distinct objects:

$ echo '{"arguments":{},"result":"success"} {"port":37482}' | jq -s '.'
[
  {
    "arguments": {},
    "result": "success"
  },
  {
    "port": 37482
  }
]

You must then address the second element of the array (.[1]), and subsequently the 'port' element (.[1].port).

---

As an extension to address some of your further questions:

You do know what the JSON is, you grab it here, and could easily print it, redirect it to a file, etc...

client_id=$(cat "$client_id_file")
curl "http://209.222.18.222:2000/?client_id=$client_id" > EXAMPLE.json

I've identified a method to extract the port number above, but if you can't / don't want to use jq, then python would work nicely, but unfortunately your input appears to be not-quite-JSON, so we need to work a bit harder:

Note: we need to pass the JSON in as the first argument, as the script is going in via stdin, so the echo xxx | jq approach above won't work nicely.

$ python - <<"EOF" '{"arguments":{},"result":"success"} {"port":37482}'
def read_obj(filename):
    from sys import argv
    from json import JSONDecoder
    decoder = JSONDecoder()
    file_content = argv[1].lstrip()
    while file_content:
        obj, eod = decoder.raw_decode(file_content)
        file_content = file_content[eod:].lstrip()
        yield obj

x = read_obj('x')
obj = next(x) # discard the first object
obj = next(x) # use the second object
print(obj['port'])
EOF

I can't help you interface with transmission.

Answer 2

Success! Working script below:

Dependencies: transmission-remote - you can install the transmission-remote-openssl package through optware. sha256sum - optware package coreutils-sha256sum

#!/usr/bin/env bash
#
# Enable port forwarding when using Private Internet Access
#
# Usage:
#  ./port_forwarding.sh
# script must be run within 2 mins of connecting to vpn server. Do not forget to reconnect/connect
# fill in your transmission username, password and hostname/ip below:

TRANSUSER=xxxxx
TRANSPASS=xxxxx
TRANSHOST=localhost
#now let the script do the work

Sleep 20
echo pausing to wait for vpn to connect and transmission to start

error( )
{
  echo "$@" 1>&2
  exit 1
}

error_and_usage( )
{
  echo "$@" 1>&2
  usage_and_exit 1
}

usage( )
{
  echo "Usage: `dirname $0`/$PROGRAM"
}

usage_and_exit( )
{
  usage
  exit $1
}

version( )
{
  echo "$PROGRAM version $VERSION"
}


port_forward_assignment( )
{
  client_id_file="/etc/openvpn/pia_client_id"
  if [ ! -f "$client_id_file" ]; then
    if hash shasum 2>/dev/null; then
      head -n 100 /dev/urandom | shasum -a 256 | tr -d " -" > "$client_id_file"
    elif hash sha256sum 2>/dev/null; then
      head -n 100 /dev/urandom | sha256sum | tr -d " -" > "$client_id_file"
    else
      echo "Please install shasum or sha256sum, and make sure it is visible in your \$PATH"
      exit 1
    fi
  fi
  client_id=`cat "$client_id_file"`
  json=`curl "http://209.222.18.222:2000/?client_id=$client_id" 2>/dev/null`
  if [ "$json" == "" ]; then
    json='Port forwarding is already activated on this connection, has expired, or you are not connected to a PIA region that supports port forwarding'
  fi

  echo server returned: $json

#trim VPN forwarded port from JSON
PORT=$(echo $json | awk 'BEGIN{r=1;FS="[{}\":]+"} /port/{r=0; print $3} END{exit r}')
echo if successful, trimmed port is:$PORT

#change transmission port on the fly

transmission-remote $TRANSHOST --auth $TRANSUSER:$TRANSPASS -p "$PORT"
echo here are your transmission credentials: host:$TRANSHOST username:$TRANSUSER password:$TRANSPASS
}
echo remember to run no longer than 2 mins after reconnecting/connecting to vpn server.

EXITCODE=0
PROGRAM=`basename $0`
VERSION=2.1

while test $# -gt 0
do
  case $1 in
  --usage | --help | -h )
    usage_and_exit 0
    ;;
  --version | -v )
    version
    exit 0
    ;;
  *)
    error_and_usage "Unrecognized option: $1"
    ;;
  esac
  shift
done

port_forward_assignment

exit 0