diff -upr Shorewall-core.orig/configure Shorewall-core/configure
--- Shorewall-core.orig/configure	2020-09-25 01:02:15.000000000 +0300
+++ Shorewall-core/configure	2024-02-01 05:59:53.741774754 +0200
@@ -134,7 +134,7 @@ if [ -z "$vendor" ]; then
 	*)
 	    if [ -f /etc/debian_version ]; then
 		params[HOST]=debian
-		ls -l /sbin/init | fgrep -q systemd &&  rcfile=shorewallrc.debian.systemd || rcfile=shorewallrc.debian.sysvinit
+		ls -l /sbin/init | grep -F -q systemd &&  rcfile=shorewallrc.debian.systemd || rcfile=shorewallrc.debian.sysvinit
 	    elif [ -f /etc/altlinux-release ] ; then
 		params[HOST]=alt
 	    elif [ -f /etc/redhat-release ]; then
@@ -163,7 +163,7 @@ else
     if [ $vendor = linux ]; then
 	rcfile=shorewallrc.default;
     elif [ $vendor = debian -a -f /etc/debian_version ]; then
-	ls -l /sbin/init | fgrep -q systemd && rcfile=shorewallrc.debian.systemd || rcfile=shorewallrc.debian.sysvinit
+	ls -l /sbin/init | grep -F -q systemd && rcfile=shorewallrc.debian.systemd || rcfile=shorewallrc.debian.sysvinit
     else
 	rcfile=shorewallrc.$vendor
     fi
diff -upr Shorewall-core.orig/lib.cli Shorewall-core/lib.cli
--- Shorewall-core.orig/lib.cli	2020-09-25 00:46:24.000000000 +0300
+++ Shorewall-core/lib.cli	2024-02-01 06:00:01.688623248 +0200
@@ -252,7 +252,7 @@ show_one_classifier() {
 
     qt tc -s filter ls root dev $1 && tc -s filter ls root dev $device | grep -v '^$'
     tc filter show dev $1
-    tc class show dev $1 | fgrep 'leaf ' | fgrep -v ' hfsc' | sed 's/^.*leaf //;s/ .*//' | while read class; do
+    tc class show dev $1 | grep -F 'leaf ' | grep -F -v ' hfsc' | sed 's/^.*leaf //;s/ .*//' | while read class; do
 	if [ -n "$class" ]; then
 	    echo
 	    echo Node $class
@@ -426,7 +426,7 @@ resolve_arptables() {
 savesets() {
     local supported
 
-    supported=$(run_it $g_firewall help | fgrep savesets )
+    supported=$(run_it $g_firewall help | grep -F savesets )
 
     [ -n "$supported" ] && run_it $g_firewall savesets ${g_restorepath}-ipsets 
 }
@@ -437,7 +437,7 @@ savesets() {
 savesets1() {
     local supported
 
-    supported=$(run_it $g_firewall help | fgrep savesets )
+    supported=$(run_it $g_firewall help | grep -F savesets )
 
     [ -n "$supported" ] && run_it $g_firewall savesets ${VARDIR}/ipsets.save && progress_message3 "The ipsets have been saved to ${VARDIR}/ipsets.save"
 }
@@ -696,7 +696,7 @@ find_sets() {
     local junk
     local setname
 
-    $IPSETN -L | egrep "^Name: ${1}(_.+)?$" | while read junk setname; do echo $setname; done
+    $IPSETN -L | grep -E "^Name: ${1}(_.+)?$" | while read junk setname; do echo $setname; done
 }
 
 list_zone() {
@@ -707,9 +707,9 @@ list_zone() {
     determine_ipset_version
 
     if [ $g_family -eq 4 ]; then
-	sets=$($IPSETN -L | egrep "^$1(_.+)?");
+	sets=$($IPSETN -L | grep -E "^$1(_.+)?");
      else
-	sets=$($IPSETN -L | egrep "^6_$1(_.+)?")
+	sets=$($IPSETN -L | grep -E "^6_$1(_.+)?")
     fi
 
     [ -n "$sets" ] || sets=$(find_sets $1)
@@ -1207,7 +1207,7 @@ show_ipsec() {
     $IP -s -$g_family xfrm policy | spd_filter
 
     heading "PFKEY SAD"
-    $IP -s -$g_family xfrm state | egrep -v '[[:space:]]+(auth-trunc|enc )' # Don't divulge the keys
+    $IP -s -$g_family xfrm state | grep -E -v '[[:space:]]+(auth-trunc|enc )' # Don't divulge the keys
 }
 
 show_ipsec_command() {
@@ -1533,7 +1533,7 @@ show_command() {
 	    if chain_exists dynamic; then
 		g_ipt_options="$g_ipt_options --line-numbers"
 		$g_tool -t filter -L dynamic $g_ipt_options  | head -n2
-		$g_tool -t filter -L dynamic $g_ipt_options  | fgrep ACCEPT | $output_filter
+		$g_tool -t filter -L dynamic $g_ipt_options  | grep -F ACCEPT | $output_filter
 	    fi
 	    ;;
 	ipsec)
@@ -1625,7 +1625,7 @@ perip_accounting() {
 
 	if [ -n "$hnames" ]; then
 	    for hname in $hnames; do
-		iptaccount -l $hname | egrep '^IP:|^Show'
+		iptaccount -l $hname | grep -E '^IP:|^Show'
 		echo
 	    done
 	else
@@ -3253,7 +3253,7 @@ determine_capabilities() {
 
 	if $TC filter add basic help 2>&1 | grep -q ^Usage; then
 	    BASIC_FILTER=Yes
-	    $TC filter add basic help 2>&1 | egrep -q match && BASIC_EMATCH=Yes
+	    $TC filter add basic help 2>&1 | grep -E -q match && BASIC_EMATCH=Yes
 	fi
 
 	if $TC action add connmark help 2>&1 | grep -q ^Usage; then
@@ -3674,7 +3674,7 @@ blacklist_command() {
     if [ $COMMAND = 'blacklist!' ]; then
 	timeout='timeout 0'
     else
-	echo "$@" | fgrep -q ' timeout ' || timeout="timeout $g_dbltimeout"
+	echo "$@" | grep -F -q ' timeout ' || timeout="timeout $g_dbltimeout"
     fi
 
     if $IPSET -A $g_blacklistipset $@ $timeout -exist; then
@@ -4932,12 +4932,12 @@ shorewall_cli() {
 		#
 		# First look for it here
 		#
-		if type $1 2> /dev/null | fgrep -q 'is a function'; then
+		if type $1 2> /dev/null | grep -F -q 'is a function'; then
 		    #
 		    # It's a shell function -- call it
 		    #
 		    $@
-		elif type $1 2> /dev/null | fgrep -q 'is a shell function'; then
+		elif type $1 2> /dev/null | grep -F -q 'is a shell function'; then
 		    #
 		    # It's a shell function -- call it
 		    #
diff -upr Shorewall-core.orig/lib.common Shorewall-core/lib.common
--- Shorewall-core.orig/lib.common	2020-09-25 00:46:24.000000000 +0300
+++ Shorewall-core/lib.common	2024-02-01 05:59:46.108265163 +0200
@@ -639,7 +639,7 @@ find_first_interface_address_if_any() #
 #Determines if the passed interface is a loopback interface
 #
 loopback_interface() { #$1 = Interface name
-    [ "$1" = lo ] || $IP link show $1 | fgrep -q LOOPBACK
+    [ "$1" = lo ] || $IP link show $1 | grep -F -q LOOPBACK
 }
 
 #
@@ -648,7 +648,7 @@ loopback_interface() { #$1 = Interface n
 find_loopback_interfaces() {
     local interfaces
 
-    [ -x "$IP" ] && interfaces=$($IP link show | fgrep LOOPBACK | sed 's/://g' | cut -d ' ' -f 2)
+    [ -x "$IP" ] && interfaces=$($IP link show | grep -F LOOPBACK | sed 's/://g' | cut -d ' ' -f 2)
 
     [ -n "$interfaces" ] && echo $interfaces || echo lo
 }