mesg: add page (#3001)

pages/linux/mesg.md

@@ -0,0 +1,16 @@
+# mesg
+
+> Check or set a terminal's ability to receive messages from other users, usually from the write command.
+> See also `write`.
+
+- Check terminal's openness to write messages:
+
+`mesg`
+
+- Disable receiving messages from the write command:
+
+`mesg n`
+
+- Enable receiving messages from the write command:
+
+`mesg y`