When a command is entered at the TCL prompt, the system saves the command in the TCL stack file of the dm account. Your stack is not terminal dependent. If you leave a terminal without logging off, another user can use the terminal under your user-ID. This causes the new user to step-on the stack.
Changing any part of a TCL command in the stack, causes that stack entry to be moved to the top of the stack. This feature tends to keep the stack compact. The fact that only unique commands are saved also helps keep the stack compact. Unique, in this context, means that there are never any duplicated commands in the stack. For example, even if the who command had been used many times, it only displays once in the stack. Each time a command is found and re-executed, it is moved to the top of the stack.
However, the TCL stack does not have a maximum number of entries and can continue to grow indefinitely. Therefore, from time to time, the stack should be reduced either from TCL or by using the u (update) command to modify the actual stack item (u dm,tcl-stack, user-ID).
Since the TCL stack is an updated file, it is frequently locked and updated by the system. If two users share the same user-ID, then while the first user types a TCL command, the second user is locked-out of the TCL stack, and their terminal beeps as long as the first user is still entering the command.
The stacker allows new commands even if the stack item is locked by another port.
When editing the TCL command stack item, it is possible to cut and paste and stack data or additional commands under the TCL statement. Use the CTRL+V command to stack data or additional commands.
These are a few of the Update commands that can be used to move through a stack to retrieve and run previously entered commands:
| CTRL+A | Searches for the entered string. |
| CTRL+D | Returns to the previous command in the stack. |
| CTRL+E | If the cursor is on the first character, deletes the entry from the stack and displays the next command down the stack; otherwise deletes to the end of the command. |
| CTRL+F | Goes forward to the next command up in the stack. |
| CTRL+P | Moves a duplicate copy of the current TCL command at the current position in the stack to the top of the stack. |
| CTRL+X | Clears the displayed command from the screen and moves the pointer back to the top of the stack. |
| CTRL+Z | Returns to the command at the top of the stack. |
| CTRL+ZA | Same as CTRL+A, but searches to the top of the stack. |