EOF
Checks to see if the end of an open file has been reached
result = EOF( filenum )
Returns true (-1) if end-of-file has been reached, zero (0) otherwise.
When reading from files opened for Input (File Mode), it is useful to know when the end of the file has been reached, thus avoiding errors caused by reading past the ends of files. Use EOF to determine this. EOF expects a valid file number from an already opened file. Use FreeFile to retrieve an available file file number.
For file numbers bound to files opened for Output, EOF always returns 0.
Because of underlying differences in the libraries used by the compiler on different platforms, the EOF function can be unreliable when reading text files created in Linux (with LF line endings) in the Windows version of the compiler. The DOS and Linux compilers do not have this problem. One solution is to open the file for Binary access instead of for Input. Line Input# and EOF can still be used as in the above example, and the EOF function will work reliably. This solution will not detect the end of file character, but this is only used to mark the end of text streams that are not disk files.
Syntax
Usage
result = EOF( filenum )
Parameters
Return Value
Returns true (-1) if end-of-file has been reached, zero (0) otherwise.
Description
When reading from files opened for Input (File Mode), it is useful to know when the end of the file has been reached, thus avoiding errors caused by reading past the ends of files. Use EOF to determine this. EOF expects a valid file number from an already opened file. Use FreeFile to retrieve an available file file number.
For file numbers bound to files opened for Output, EOF always returns 0.
Example
'' This code finds a free file number to use and attempts to open the file
'' "file.ext" and if successful, binds our file number to the opened file. It
'' reads the file line by line, outputting it to the screen. We loop until eof()
'' returns true, in this case we ignore the loop if file is empty.
Dim As String file_name
Dim As Integer file_num
file_name = "file.ext"
file_num = FreeFile( ) '' retrieve an available file number
'' open our file and bind our file number to it, exit on error
If( Open( file_name For Input As #file_num ) ) Then
Print "ERROR: opening file " ; file_name
End -1
End If
Do Until EOF( file_num ) '' loop until we have reached the end of the file
Dim As String text
Line Input #file_num, text '' read a line of text ...
Print text '' ... and output it to the screen
Loop
Close #file_num '' close file via our file number
End 0
'' "file.ext" and if successful, binds our file number to the opened file. It
'' reads the file line by line, outputting it to the screen. We loop until eof()
'' returns true, in this case we ignore the loop if file is empty.
Dim As String file_name
Dim As Integer file_num
file_name = "file.ext"
file_num = FreeFile( ) '' retrieve an available file number
'' open our file and bind our file number to it, exit on error
If( Open( file_name For Input As #file_num ) ) Then
Print "ERROR: opening file " ; file_name
End -1
End If
Do Until EOF( file_num ) '' loop until we have reached the end of the file
Dim As String text
Line Input #file_num, text '' read a line of text ...
Print text '' ... and output it to the screen
Loop
Close #file_num '' close file via our file number
End 0
Because of underlying differences in the libraries used by the compiler on different platforms, the EOF function can be unreliable when reading text files created in Linux (with LF line endings) in the Windows version of the compiler. The DOS and Linux compilers do not have this problem. One solution is to open the file for Binary access instead of for Input. Line Input# and EOF can still be used as in the above example, and the EOF function will work reliably. This solution will not detect the end of file character, but this is only used to mark the end of text streams that are not disk files.
Differences from QB
- In QB the comm port signaled an EOF when there were no chars waiting to be read.
- In QB, for files opened in RANDOM or BINARY mode, EOF returned non-zero only after a read past the end of file has been attempted. In FreeBASIC, EOF returns true after the last item is read.
See also
