fix: prefer using iproute2 instead of ifconfig

For `_comp_compgen_available_interfaces`, we prefer to use ip
(iproute) since long interface names will be truncated by ifconfig
(respective packages in the operating system, e.g. inetutils) [1].
Even for the other functions that use "ifconfig" and "ip", we change
to use `ip` because `ip`'s behavior is more uniform among the systems
and also `ip` is becoming more common in Linux distributions.

[1]: https://github.com/scop/bash-completion/pull/1090/files

Co-authored-by: Koichi Murase <myoga.murase@gmail.com>

bash_completion

@@ -1626,7 +1626,7 @@ _comp_compgen_mac_addresses()
     # - ip link: link/ether
     _comp_compgen -v addresses split -- "$(
         {
-            LC_ALL=C ifconfig -a || ip -c=never link show || ip link show
+            ip -c=never link show || ip link show || LC_ALL=C ifconfig -a
         } 2>/dev/null | command sed -ne \
             "s/.*[[:space:]]HWaddr[[:space:]]\{1,\}\($_re\)[[:space:]].*/\1/p" -ne \
             "s/.*[[:space:]]HWaddr[[:space:]]\{1,\}\($_re\)[[:space:]]*$/\1/p" -ne \
@@ -1697,7 +1697,7 @@ _comp_compgen_ip_addresses()
     local PATH=$PATH:/sbin
     local addrs
     _comp_compgen -v addrs split -- "$({
-        LC_ALL=C ifconfig -a || ip -c=never addr show || ip addr show
+        ip -c=never addr show || ip addr show || LC_ALL=C ifconfig -a
     } 2>/dev/null |
         command sed -e 's/[[:space:]]addr:/ /' -ne \
             "s|.*inet${_n}[[:space:]]\{1,\}\([^[:space:]/]*\).*|\1|p")" ||
@@ -1731,9 +1731,12 @@ _comp_compgen_available_interfaces()
         if [[ ${1-} == -w ]]; then
             iwconfig
         elif [[ ${1-} == -a ]]; then
-            ifconfig || ip -c=never link show up || ip link show up
+            # Note: we prefer ip (iproute2) to inetutils (ifconfig) since long
+            # interface names will be truncated by ifconfig [1].
+            # [1]: https://github.com/scop/bash-completion/issues/1089
+            ip -c=never link show up || ip link show up || ifconfig
         else
-            ifconfig -a || ip -c=never link show || ip link show
+            ip -c=never link show || ip link show || ifconfig -a
         fi
     } 2>/dev/null | _comp_awk \
         '/^[^ \t]/ { if ($1 ~ /^[0-9]+:/) { print $2 } else { print $1 } }')" &&

test/fixtures/shared/bin/ip

@@ -0,0 +1,36 @@
+#!/bin/sh
+
+# Dummy "ip addr show" and "ip link show up" emulator
+
+for arg in "$@"; do
+case "$arg" in
+link)
+cat <<EOF
+1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
+    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
+2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT group default 
+    link/ether 33:33:33:33:33:33 brd ff:ff:ff:ff:ff:ff link-netnsid 0
+EOF
+exit 0
+  ;;
+addr)
+cat <<EOF
+1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
+    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
+    inet 127.0.0.1/8 scope host lo
+       valid_lft forever preferred_lft forever
+    inet6 ::1/128 scope host 
+       valid_lft forever preferred_lft forever
+2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default 
+    link/ether 33:33:33:33:33:33 brd ff:ff:ff:ff:ff:ff link-netnsid 0
+    inet 192.168.80.11/24 brd 192.168.80.255 scope global eth0
+       valid_lft forever preferred_lft forever
+    inet6 fe80::000:0000:0000:0000/64 scope link 
+       valid_lft forever preferred_lft forever
+EOF
+exit 0
+  ;;
+esac
+done
+
+exit 1