at: add page, atq: add page, atrm: add page, and batch: add page (#1344)

commands to queue commands execution at specified time
or when system load allows

pages/common/batch.md

@@ -0,0 +1,16 @@
+# batch
+
+> Execute commands at a later time when the system load levels permit.
+> Service atd (or atrun) should be running for the actual executions.
+
+- Execute a command from standard input:
+
+`echo "{{./make_db_backup.sh}}" | batch`
+
+- Execute commands from a given file:
+
+`batch -f {{path/to/file}}`
+
+- Execute commands from standard input (press `Ctrl + D` when finished):
+
+`batch`