yf_get_ip_address.function

#! /bin/true
# vi: set tabstop=4 syntax=sh : # colorize it in 'vi' and use shorter tabstops
# SPDX-License-Identifier: GPL-2.0-or-later
#######################################################################################
#                                                                                     #
# get_ip_address - retrieve the IPv4 addresses for the specified interface            #
#                                                                                     #
# parameters:                                                                         #
#   $1 - interface to be used                                                         #
#                                                                                     #
# stdout:                                                                             #
#   a list of IPv4 addresses available at the interface                               #
#                                                                                     #
# return code:                                                                        #
#   0 - stdout is valid and contains at least one entry                               #
#   1 - the interface name is invalid or the interface has no IPv4 address assigned   #
#                                                                                     #
# WARNING:                                                                            #
# This script needs a 'ip' binary, which isn't part of POSIX standards.               #
#                                                                                     #
#######################################################################################
#                                                                                     #
# U: ip sed printf                                                                    #
# W: -                                                                                #
# F: -                                                                                #
# I: -                                                                                #
# K: network                                                                          #
#                                                                                     #
#######################################################################################
yf_get_ip_address()
(
	intf="$1"
	addrs="$(ip -o -f inet addr show dev $intf 2>/dev/null | sed -n -e "s|^[0-9]*: $intf.*inet \([0-9./]*\).*|\1|p")"
	[ ${#addrs} -eq 0 ] && return 1
	printf "$addrs"
	return 0
)