new tool: fqdn

.vscode/extensions.json

@@ -1,7 +1,6 @@
 {
   "recommendations": [
     "mads-hartmann.bash-ide-vscode",
-    "rogalmic.bash-debug",
+    "rogalmic.bash-debug"
-    "mkhl.shfmt",
   ],
 }

tools/fqdn

@@ -0,0 +1,90 @@
+#!/usr/bin/env bash
+
+# CONSTANTS
+
+BASEDIR=$(dirname "$0")
+COMMAND=show
+
+# FUNCTIONS
+function usage {
+    echo "usage: $(basename "$0") [--set NEW_FQDN]"
+    echo "       either returns the fully qualified name when pass with no argument"
+    echo "       or define the new fully qualified name when pass --set {NEW_FQDN}"
+}
+
+function parse_options {
+    while [[ $# -gt 0 ]]; do
+        case "$1" in
+        '--set')
+            COMMAND=define
+            shift 1
+            [[ -z ${1:-} || $1 =~ ^- ]] && usage && exit 1
+            NEW_FQDN=$1
+            ;;
+        --help | -h)
+            usage && exit 0
+            ;;
+        *)
+            echo >&2 "Unknown option: $1" && usage && exit 2
+            ;;
+        esac
+
+        shift 1 # Move to the next argument
+    done
+}
+
+function show {
+    hostname -f
+}
+
+function define {
+    if [[ $NEW_FQDN == *.* ]]; then
+        name=$(echo $NEW_FQDN | cut -d. -f1)
+        domain=${NEW_FQDN#${name}.}
+        if [[ -n $domain ]]; then
+            define_fqdn $name $domain
+        else
+            define_single $name
+        fi
+    else
+        define_single $NEW_FQDN
+    fi
+}
+
+function define_single {
+    local single=$1
+    local previous=$(hostname -f)
+    for i in $(grep $previous /etc/hosts | cut -f1); do
+        append_or_replace ^$i.* "$i\t$single" /etc/hosts >/dev/null
+    done
+    hostnamectl hostname $single
+}
+
+function define_fqdn {
+    local name=$1
+    local domain=$2
+    local previous=$(hostname -f)
+
+    for i in $(grep $previous /etc/hosts | cut -f1); do
+        append_or_replace ^$i.* "$i\t$name.$domain $name" /etc/hosts >/dev/null
+    done
+    hostnamectl hostname $name
+}
+
+function perform_command {
+    case $COMMAND in
+    show)
+        show
+        ;;
+    define)
+        [[ $(id -u) != 0 ]] && echo 'require root privilege, please prepend the command with `sudo`' && exit 10
+        define
+        ;;
+    esac
+}
+
+# MAIN
+
+set -Eue
+parse_options $*
+perform_command