![]() See Understanding (LUNs) for additional information on LUNs. ![]() Letting IDL assign the LUN from the list of free unit numbers ensures that your application does not attempt to use a LUN already in use by someone else’s application. By using the GET_LUN keyword to the OPEN routines, you can ask IDL to assign a free Logical Unit Number between 100-128 to the specified file. ![]() ![]() While it is possible to assign any of the integers between 1-99 to a given file, when writing applications for others it is good programming practice to let IDL assign and manage the LUNs itself. There are a total of 128 LUNs available for assignment to files. Logical Unit Numbers (LUNs) are assigned to individual files when the files are opened by the IDL OPENR/OPENU/OPENW commands, and are used to specify which file IDL should read from or write to. Logical Unit Numbers and Application Development OPENU (OPEN Update) opens an existing file for input and output.If the file exists, it is truncated and its old contents are destroyed. OPENW (OPEN Write) opens a new file for input and output.OPENR (OPEN Read) opens an existing file for input only.The three OPEN procedures open a specified file for input and/or output. ![]()
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