VMD User's Guide

Chapter 8Tcl Text InterfaceThe Tcl text interface provides complete access to all the VMD commands. Anything that can bedone from the menus can be done with VMD text commands.8.1 Using text commandsText commands can be entered into VMD in several ways:• Commands can be entered by typing them at the VMD prompt in the text console window.This window normally contains the prompt vmd > . When other text (e.g., from a mousepick) is displayed to the screen, it will scroll the screen up so the prompt is not at the lastline of the screen. To make it reappear, press enter. When entering multi-line commands,an alternate prompt appears, ? , and will not disappear until the command is finished.Sometimes it is waiting for a close to a double quote, open brace, or open bracket, while atother times it is waiting for a line that doesn’t end in a backslash.• Since you may not want to retype all the data in every time, there are two ways to read thedata in from a text file. One is the play command. This reads a line from the file, executesit, then updates the screen and checks for any changes in the mouse or forms input, so thatVMD stays interactive during execution of the script. The second way is the Tcl commandsource. This reads the whole file before allowing the mouse and forms to respond to newinput. This is often more efficient when your script contains many lines.• On Unix/Linux platforms, if the file .vmdrc (see section 12.3.3) exists in your home directory,it is played at VMD startup. If you don’t have a .vmdrc file, VMD uses a default script inthe VMD installation directory. Similarly, at startup the -e command line flag can be usedto specify an input file to be played after reading the .vmdrc file. The Windows version ofVMD works similarly, though the startup file is named vmd.rc.A good use of the .vmdrc file is to specify which VMD menus you would like to have openwhen you start VMD and where they should be placed; see section 8.3.18) for information onusage.89