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IDL Reference Guide: Procedures and Functions

EOF

The EOF function tests the specified file unit for the end-of-file condition.

Note
The EOF function cannot be used with files opened with the RAWIO keyword to the OPEN routines. Many of the devices commonly used with RAWIO signal their end-of-file by returning a zero transfer count to the I/O operation that encounters the end-of-file.

Syntax

Result = EOF(Unit)

Return Value

If the file pointer is positioned at the end of the file, EOF returns true (1), otherwise false (0) is returned.

Arguments

Unit

The file unit to test for end-of-file.

Keywords

None.

Examples

If file unit number 1 is open, the end-of-file condition can be checked by examining the value of the expression EOF(1). For example, the following IDL code reads and prints a text file:

; Open the file test.lis:  
OPENR, 1, 'test.lis'  
; Define a string variable:  
A = ''  
; Loop until EOF is found:  
WHILE ~ EOF(1) DO BEGIN  
   ; Read a line of text:  
   READF, 1, A  
   ; Print the line:  
   PRINT,   
ENDWHILE  
; Close the file:  
CLOSE, 1

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