systemctl-is-active: add page (#18434)

pages/linux/systemctl-is-active.md

@@ -0,0 +1,20 @@
+# systemctl is-active
+
+> Check if one or more systemd units are active.
+> More information: <https://www.freedesktop.org/software/systemd/man/latest/systemctl.html#is-active%20PATTERN%E2%80%A6>.
+
+- Check whether a unit is active:
+
+`systemctl is-active {{unit}}`
+
+- Check whether multiple units are active:
+
+`systemctl is-active {{unit1 unit2 ...}}`
+
+- Check whether a unit is active without printing the state to `stdout`:
+
+`systemctl is-active {{[-q|--quiet]}} {{unit}}`
+
+- Check whether a user unit is active:
+
+`systemctl is-active --user {{unit}}`