# Linux ## User Switching ```bash sudo -u user command # run command as another user ``` ## Job Control See [[Bash and Zsh#Job Control]] — covers `jobs`, `bg`, `fg`, `disown`, and `Ctrl+Z`. ## Pipes — stderr vs stdout ```bash command 2>&1 | next # pipe both stdout and stderr command 2>/dev/null # discard stderr command 2>&1 1>/dev/null # pipe only stderr ``` ## Terminal Messaging ### wall — Broadcast Messages ```bash wall "System going down in 10 minutes" wall /path/to/message.txt ``` | Option | Description | |--------|-------------| | `-n, --nobanner` | Suppress sender/date banner | | `-t, --timeout <s>` | Max wait per terminal write (default: 300) | | `-g, --group <grp>` | Send only to group members | Only superusers can write to terminals of users who blocked messages. Lines wrap at 79 characters. ### mesg — Control Message Reception ```bash mesg # show current status mesg y # allow messages mesg n # block messages ``` ### talk — Interactive Chat Split-screen terminal chat between two users: ```bash talk username # same machine talk user@host # remote host ``` - `Ctrl+L` — repaint screen - `Ctrl+C` — exit conversation The recipient must have `mesg y` enabled. --- See also: [[VPS Setup]]