diff --git a/lib/db.sh b/lib/db.sh
new file mode 100644
index 0000000..3d90a80
--- /dev/null
+++ b/lib/db.sh
@@ -0,0 +1,62 @@
+#!/bin/bash
+
+FILE_TRASH="/dev/null"
+DB_PATH="./data/"
+SED_DARWIN="''"
+
+
+# errors :
+# 1 file do not exist
+# 2 entry do not exist
+#
+# ok :
+# 0 entry exist
+function check_in_db {
+
+    db_name="${1}"
+    search_id="${2}"
+
+    [ -f "${DB_PATH}${db_name}.db" ] || return 1
+    cat "${DB_PATH}${db_name}.db" | \
+      grep -E "^${search_id}" > "${FILE_TRASH}" || return 2
+    return 0
+}
+
+function add_in_db {
+
+    db_name="${1}"
+    shift 1
+    
+    local IFS=";"
+    echo add
+    echo "$*" >> ${DB_PATH}${db_name}.db
+    return 0
+
+}
+
+function delete_in_db {
+
+    db_name="${1}"
+    id="${2}"
+
+    sed -i ${SED_DARWIN} "/^${id}/d" "${DB_PATH}${db_name}.db"
+    return 0
+
+}
+
+# errors :
+# 0 file do not exist
+#
+# ok :
+# [1-500] entry count
+function count_in_db {
+
+    db_name="${1}"
+    id="${2}"
+
+    [ -f "${DB_PATH}${db_name}.db" ] || return 0
+    count=$(cat "${DB_PATH}${db_name}.db" | grep "${id}" | wc -l | sed -e 's/ //g')
+
+    return "${count}"
+
+}
\ No newline at end of file