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|
#!/bin/sh
set -eu
usage() {
cat <<-'EOF'
Usage:
free-port
free-port -h
EOF
}
help() {
cat <<-'EOF'
Options:
-h, --help show this message
Returns a free TCP port.
Examples:
Get a port for a command:
$ cmd -p `free-port`
EOF
}
for flag in "$@"; do
case "$flag" in
(--)
break
;;
(--help)
usage
help
exit
;;
(*)
;;
esac
done
while getopts 'h' flag; do
case "$flag" in
(h)
usage
help
exit
;;
(*)
usage >&2
exit 2
;;
esac
done
shift $((OPTIND - 1))
MIN_PORT=1024
MAX_PORT=65536
gen_port() {
shuf -n1 -i "${MIN_PORT}-${MAX_PORT}"
}
while true; do
PORT="$(gen_port)"
if ! lsof -s TCP:LISTEN -i ":$PORT" >/dev/null; then
break
fi
done
printf '%s\n' "$PORT"
|
