OPENUP Function

OPENUP(string-expression)

Opens a file for input and output (reading and writing). Returns an integer file handle that must be used with READ$ Function$ "READ\$", WRITE, and CLOSE.

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Examples

REM Open an existing file for update
fh = OPENUP("/data/config.txt")
IF fh < 0 THEN
    PRINT "Could not open file"
    END
ENDIF
 
REM Read the first line
line$ = READ$(fh)
PRINT "First line: "; line$
 
REM Write new content
WRITE fh, "Updated value"
CLOSE fh

REM Create a file if it doesn't exist
fh = OPENUP("/data/newfile.txt")
IF fh >= 0 THEN
    WRITE fh, "Initial content"
    CLOSE fh
ENDIF

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Notes

• Provides both read and write access to the file.
• Returns a non-negative handle on success, or a negative value on failure.
• Unlike OPENOUT, this does not always truncate the file; content may be preserved.
• File handle must be closed with CLOSE.
• Use with EOF to detect the end of file during reads.

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See also: READ$ · WRITE · CLOSE · OPENIN · OPENOUT