Check for available usernames

open_users.sh

#!/bin/bash

# Check at least one argument is passed.
if [ $# -eq 0 ]
then
  echo "Usage: ./open-users.sh [website URL]"
  exit 1
fi

URL=$1
NAME=$(basename "$0" .sh)
TMP_FILE=$(mktemp /tmp/"$NAME".XXXXXX)
LOG_FILE=$(date +"%m-%d-%Y-%H:%M:%S-openusers.log")
export LOG_FILE # Allows check_name function to access.

echo "Username combinations stored at $TMP_FILE"
echo "Logging to $LOG_FILE"

# Generate all 3 alphanumeric combinations.
for first in {a..z} {0..9}; do
  for second in {a..z} {0..9}; do
    for third in {a..z} {0..9}; do
        echo "https://$URL/$first$second$third" >> "$TMP_FILE"
    done
  done
done

# Shuffle the username combinations.
gshuf "$TMP_FILE" -o "$TMP_FILE"

# Takes a URL, then writes to stdout and a log file if response is not 200.
check_name() {
    FULL_URL=$0
    RES_CODE=$(curl -o /dev/null -L -s -w "%{http_code}" -A "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_6) AppleWebKit/603.3.8 (KHTML, like Gecko)" "$FULL_URL")
    if [ "$RES_CODE" -ne "200" ]; then
      echo "$FULL_URL $RES_CODE" | tee -a "$LOG_FILE"
    fi
}
export -f check_name

# You can speed this up but servers may respond back with HTTP status code 429
xargs -n1 -P1 bash -c 'check_name "$@"' < "$TMP_FILE"