AWK to get details from /proc/net/tcp and /proc/net/udp when netstat and lsof are not available

awk_netstat.sh

#! /bin/env bash

# Install
# - Get the "raw" link for the most current SHA of the file
# - Use that to download the file and chmod +x it to make it executable

# e.g.
# curl -o awk_netstat.sh https://gist.githubusercontent.com/.../awk_netstat.sh
# chmod +x awk_netstat.sh

# Usage
# ./awk_netstat $(cat /var/run/nginx.pid) | wc -l

# Based on gists
# - https://gist.github.com/staaldraad/4c4c80800ce15b6bef1c1186eaa8da9f
#   - added TCP states
# - https://gist.github.com/qistoph/1b0708c888f078c3720de6c6f9562997


# Check if at least one argument is provided
if [ $# -eq 0 ]; then
    echo "Usage: $0 <pid> [additional arguments...]"
    exit 1
fi

# Get the PID from the first argument
PID="$1"
shift  # Remove the first argument (PID) from the list

# Construct the command with any additional arguments
CMD="awk 'BEGIN{states[\"01\"]=\"TCP_ESTABLISHED\"
states[\"02\"]=\"TCP_SYN_SENT\"
states[\"03\"]=\"TCP_SYN_RECV\"
states[\"04\"]=\"TCP_FIN_WAIT1\"
states[\"05\"]=\"TCP_FIN_WAIT2\"
states[\"06\"]=\"TCP_TIME_WAIT\"
states[\"07\"]=\"TCP_CLOSE\"
states[\"08\"]=\"TCP_CLOSE_WAIT\"
states[\"09\"]=\"TCP_LAST_ACK\"
states[\"0A\"]=\"TCP_LISTEN\"
states[\"0B\"]=\"TCP_CLOSING\"
states[\"0C\"]=\"TCP_NEW_SYN_RECV\"
}
function hextodec(str,ret,n,i,k,c){
    ret = 0
    n = length(str)
    for (i = 1; i <= n; i++) {
        c = tolower(substr(str, i, 1))
        k = index(\"123456789abcdef\", c)
        ret = ret * 16 + k
    }
    return ret
}
function getIP(str,ret){
    ret=hextodec(substr(str,index(str,\":\")-2,2));
    for (i=5; i>0; i-=2) {
        ret = ret\".\"hextodec(substr(str,i,2))
    }
    ret = ret\":\"hextodec(substr(str,index(str,\":\")+1,4))
    return ret
}
NR > 1 {{if(NR==2)print \"Local - Remote\";local=getIP(\$2);remote=getIP(\$3)}{print local\" - \"remote\" \"states[\$4]}}' /proc/$PID/net/tcp"

# Append any additional arguments
for arg in "$@"; do
    CMD="$CMD | $arg"
done

# Execute the command
eval "$CMD"