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|
#!/usr/bin/env bash
netstat_parse_linux() {
sed -r -n 's/tcp.*\.[0-9]+:([0-9]+).*/\1/p' <<< "$1" | sort -u
}
netstat_parse_macos() {
sed -r -n 's/.*([0-9]+\.[0-9]+\.[0-9]+\.[0-9]+\.([0-9]+)).*/\2/p;s/.*\*\.([0-9]+).*/\1/p' <<< "$1" | sort -u
}
netstat_parse() {
if [[ $(uname -s) == Darwin ]]; then
netstat_parse_macos "$1"
else
netstat_parse_linux "$1"
fi
}
netstat_args="-a -t -n"
if [[ $(uname -s) == Darwin ]]; then
netstat_args="-p tcp -a -n"
fi
# Return a listing of all TCP ports in use
get_ports_tcp() {
local data=$(netstat $netstat_args)
local ports=$(netstat_parse "$data")
while read port; do
if ! [[ $port =~ ^[0-9]+$ ]]; then
continue
fi
echo "$port"
done <<< "$ports"
}
# Determine whether a port is in use
# Return
# 0 if yes
# >0 if no
get_port_status() {
local port="$1"
grep "$port" <<< $(get_ports_tcp) &>/dev/null
# returns exit code from grep
}
usage() {
printf \
"usage: %s [-h] [range_low] [range_high]
Positional arguments:
range_low (default: $PORT_MIN)
range_high (default: $PORT_MAX)
Arguments:
-h show this usage statement
" $(basename $0)
}
# main()
PORT_MIN=1024
PORT_MAX=65535
# Parse arguments
argv=($*)
argc="${#argv[@]}"
args=()
i=0
while [[ $i < $argc ]]; do
key="${argv[$i]}"
if [[ $key =~ ^- ]]; then
key="${key#-*}"
case "$key" in
h)
usage
exit 0
;;
*)
echo "error: unknown argument" >&2
usage
exit 1
;;
esac
fi
args+=("$key")
(( i++ ))
done
available=-1
range_low=${args[0]:-$PORT_MIN}
range_high=${args[1]:-$PORT_MAX}
# Check input boundaries
if (( range_low > range_high )); then
echo "Invalid port range: $range_low > $range_high" >&2
usage
exit 1
elif (( range_high < 0 )) || (( range_low < 0 )); then
echo "Range value must be a positive integer" >&2
usage
exit 1
elif (( range_high > PORT_MAX )) || (( range_low > PORT_MAX )); then
echo "Range value must be less than $PORT_MAX" >&2
usage
exit 1
fi
# Print the next available port or -1 if unable
ports=($(seq $range_low $range_high))
for port in "${ports[@]}"; do
if ! $(get_port_status $port); then
available=$port
break
fi
done
echo $available
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