Mail Bag - Why do some commands support the use of additional characters in front of their names, and others do not?
The Mail Bag has become one of my favorite new little segments on my blog, and by the number of comments that I have been getting it looks like many others agree as well. In today's Mail Bag, a reader has a question about why there are some commands that have an additional character in front of their names and there is the same command with out that additional character. For example, to plot a drawing you would use the PLOT command, but there is also a -PLOT command. Both the PLOT and -PLOT command allow you to plot a drawing, but to get to the final output from the command the process is a little bit different. The PLOT command displays a dialog box under normal situations, while the -PLOT command displays a series of command prompts to help plot a drawing. Below is a listing of a few characters that you might encounter when creating your own macros, or when you are trying to create a basic script to automate AutoCAD or AutoCAD LT.
- (Hyphen) - Command displays command prompts instead of a dialog box, in most cases the commands that support a version of the command are ones that display a dialog box. A few examples are the -PLOT vs. PLOT, -LAYER vs. LAYER, and -ARRAY vs. ARRAY commands.
+ (Plus) - There are a couple different types of commands that use the plus symbol in front of commands. The most common commands that have a plus symbol in front of their name are the ones with tabs, such as the Options dialog box or UCS dialog box. A few examples are the +OPTIONS vs. OPTIONS, +DSETTINGS vs. DSETTINGS, and +UCSMAN vs. UCSMAN commands. When the +OPTIONS is typed at the command line the prompt Tab index <0>: is displayed. If you want to display the User Preferences tab you would enter a value of 5, the leftmost tab is 0. Another version of a command that can use the plus symbol is the variation of the PUBLISH command. If a plus is placed in front of the command you are able to browse and select an existing DSD file from a standard file navigation dialog box.
' (Apostrophe) - The apostrophe symbol is used by some commands that can be used while another command is already in progress, in this state a command is known as a transparent command. Most commands can not be used transparently when other commands are running. The most commonly used commands that are used transparently are ZOOM, PAN, and -VIEW. There are many other commands that can be used transparently, as well and those are often used to control entity property settings such as COLOR, LTYPE, and SETVAR. To use a command transparently, simply start another command that displays a command prompt such as the LINE command, and then enter 'ZOOM at the command prompt while the LINE command is still in progress. AutoCAD indicates that you are in a transparent command with the display of >> in front of the command prompt. Once the transparent command has ended or been cancelled you are returned to the previous command prompt of the original command, in the example it is the LINE command.
Command: l
LINE Specify first point: 'zoom
>>Specify corner of window, enter a scale factor (nX or nXP), or
[All/Center/Dynamic/Extents/Previous/Scale/Window/Object] <real time>:
>>Press ESC or ENTER to exit, or right-click to display shortcut menu.
Resuming LINE command.
Specify first point:
Specify next point or [Undo]:
For additional information on what commands can be used transparently, which ones support a hyphen or simply a list of all commands in AutoCAD use the links below.
Transparent AutoCAD Commands
Hyphened AutoCAD Commands
AutoCAD Command Reference (R12 through 2007)
Another create feature when wanting to learn about what commands and system variables in AutoCAD is the AutoComplete feature at the command prompt. It allows you to find a command that you only remember the first few letters of. To use AutoComplete, type in the first few letters at the command prompt and press the TAB key until you find the command you are looking for. So if you wanted to know all of the commands that can use the + (plus) symbol, you can type the + symbol and then press Tab until you cycle through all the commands or until you found the one that you are interested in.
For some additional information on the AutoComplete feature see the links below:
Forgot a Command's Name, Now What?
What Was That AutoCAD System Variable or Command?
Got a question that you are looking for an answer to, send me an e-mail and I will be more than happy to help you out. Use the Email Me link below the About section on this page or click here.
Sincerely,
Lee
An updated version of my Quick Reference Guide is now available for AutoCAD 2007. The Quick Reference Guide includes information on the default Command Aliases, Accelerated Keys (Keyboard Shortcuts), Double Click Actions, Coordinate System (Types of Point Entry), Drag 'n Droppable files, Object Snaps and Selection Methods. The AutoCAD 2007 version now has two sections for Command Aliases, one for 2D and one for 3D. Other versions of the Quick Reference Guide are available starting with AutoCAD R14 through AutoCAD 2006 for download. If you have any questions just let me know, you must be a member of the HyperPics.com website in order to access the PDF file. General membership is free to everyone that signs up on the site, 
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