Merge pull request 'Add locking' (#1) from hiimgoodpack/aps:master into master

Reviewed-on: alnux/aps#1

aps.sh

@@ -4,6 +4,7 @@ AL_TEMP_LOCATION="/tmp"
 AL_INSTALL_ROOT="/tmp/alroot"
 AL_INSTALLED_PKG_DATABASE="${AL_INSTALL_ROOT}/var/aps/installed"
 AL_LOCAL_PKG_DATABASE="${AL_INSTALL_ROOT}/var/aps/repos"
+AL_LOCK="${AL_INSTALL_ROOT}/var/aps/lock"
 
 # Repo config
 official="https://git.hippoz.xyz/alnux/repo"
@@ -192,6 +193,13 @@ upgrade() {
 }
 
 main() {
+    if [ -f "${AL_LOCK}" ]; then
+        echo "[E] A lock file already exists."
+        echo "    If you're sure no package manager is running,"
+        echo "    remove the file ${AL_LOCK}"
+    fi
+    touch "${AL_LOCK}"
+
     case ${1} in
         install)
             install_local_package "${2}"
@@ -212,9 +220,12 @@ main() {
             ;;
         *)
             echo "[E] Invalid option ${1}, exiting..."
+            rm "${AL_LOCK}"
             exit 0
             ;;
     esac
+
+    rm "${AL_LOCK}"
 }
 
-main "${1}" "${2}"
+main "${1}" "${2}"