"Input Past End of File" with INPUT #; Use LINE INPUT # (82001)

MORE INFORMATION

The error "Input past end of file" (error code 62) can occur when you use the INPUT # statement in a loop to iteratively read a fixed number of values from each line of a sequential (text) file, and one of the lines in the file has the wrong number of values. This happens because INPUT # reads across line boundaries. For example, when there are too few values on a line, INPUT # continues reading values from the next line. This leaves too few values on the next line for the following INPUT # iterations. When reading the last line in the file, the error occurs.

Example Program

The program below demonstrates how INPUT # can produce "Input past end of file" due to a missing data value, and demonstrates how to use LINE INPUT # to read each line from the file and then retrieve the values from the input line.

DIM seenError%  ' tells if error "Input past end of file" occurred
CLS
q$ = CHR$(34)   ' the double-quote character (")

' Create a sequential data file with a missing value.
' The data also contains other minor problems that parseNumber
' and parseString handle better than INPUT #.
OPEN "data.txt" FOR OUTPUT AS 1
WRITE #1, 1, "two", 3    ' good data
WRITE #1, 2, "eleven"    ' missing value causes Input past end of file
PRINT #1, 3; ",,"; 10.25    ' unquoted null string
PRINT #1, 4; "eight,"; 9.5  ' good data
PRINT #1, 5; q$ + "one,"; 9 ' unmatched quote
CLOSE 1

' Read the data back from the file using INPUT #. This results in
' the error "Input past end of data" due to the missing value.
OPEN "data.txt" FOR INPUT AS 1
ON ERROR GOTO errorHandler
DO UNTIL EOF(1)
    INPUT #1, a%, b$, c#
    IF seenError% THEN
        PRINT "error"
    ELSE
        PRINT a%; "'"; b$; "'"; c#
    END IF
LOOP
ON ERROR GOTO 0
CLOSE 1

PRINT "=========="

' Read the data again using LINE INPUT #.
' The parseNumber and parseString functions print several error
' messages due to the missing value (parseNumber: null string) and
' other minor problems (unmatched ", unquoted null string).
OPEN "data.txt" FOR INPUT AS 1
DO UNTIL EOF(1)
    LINE INPUT #1, buf$
    a% = parseNumber(buf$)
    b$ = parseString(buf$)
    c# = parseNumber(buf$)
    PRINT a%; "'"; b$; "'"; c#
LOOP
CLOSE 1

END

errorHandler:
    IF ERR = 62 THEN
        ' input past end of file
        seenError% = -1
    ELSE
        ERROR ERR
    END IF
    RESUME NEXT

' parseNumber
'   Purpose
'     Retrieve and delete a numeric value from the beginning of an
'     input string. The number is terminated by a comma, space, a
'     double quote (string value), or the end of the input string. A
'     terminating comma is deleted. If no numeric value occurs before
'     the terminator, an error message is printed.
'   Parameters
'     buf$  -- the input string, modified by this function
'   Return
'     n!    -- the number retrieved
FUNCTION parseNumber! (buf AS STRING)
    DIM n AS DOUBLE      ' return value
    DIM s AS STRING      ' the value as a string
    DIM quote AS STRING  ' double quote character

    quote = CHR$(34)

    ' skip leading spaces
    DO WHILE LEFT$(buf, 1) = " "
        buf = MID$(buf, 2)
    LOOP

    ' get value into temporary string
    ' terminated by space, comma, or quote
    DO UNTIL buf = "" OR INSTR(" ," + quote, LEFT$(buf, 1))
        s = s + LEFT$(buf, 1)
        buf = MID$(buf, 2)
    LOOP
    IF s = "" THEN
        PRINT "parseNumber: null string"
        n = 0
    ELSE
        n = VAL(s)
    END IF

    ' skip trailing spaces and comma
    DO WHILE LEFT$(buf, 1) = " "
        buf = MID$(buf, 2)
    LOOP
    IF LEFT$(buf, 1) = "," THEN
        buf = MID$(buf, 2)
    END IF

    parseNumber = n
END FUNCTION

' parseString
'   Purpose
'     Retrieve and delete a string value from the beginning of an
'     input string. If the value begins with a double quote (") then
'     it is terminated by a subsequent double quote, otherwise the
'     string is terminated by a comma or the end of the input string.
'     A terminating comma is deleted. Error messages are printed if
'     the value begins with a double quote but does not end with a
'     double quote, or if an unquoted null string value occurs.
'   Parameters
'     buf$  -- the input string, modified by this function
'   Return
'     s$    -- the string retrieved
FUNCTION parseString$ (buf AS STRING)
    DIM s AS STRING         ' return value
    DIM quote AS STRING     ' double quote character
    DIM terminal AS STRING  ' close quote or comma

    quote = CHR$(34)
    s = ""

    ' skip leading spaces
    DO WHILE LEFT$(buf, 1) = " "
        buf = MID$(buf, 2)
    LOOP

    ' determine if quoted or unquoted
    IF LEFT$(buf, 1) = quote THEN
        terminal = quote
        buf = MID$(buf, 2)
    ELSE
        terminal = ","
    END IF

    ' get value
    DO UNTIL buf = "" OR LEFT$(buf, 1) = terminal
        s = s + LEFT$(buf, 1)
        buf = MID$(buf, 2)
    LOOP

    ' check closing quote
    IF terminal = quote THEN
        IF buf = "" THEN
            PRINT "parseString: unmatched " + quote + " on " + s
        ELSE
            ' skip closing quote
            buf = MID$(buf, 2)
        END IF
    ' unquoted null string not allowed
    ELSEIF s = "" THEN
        PRINT "parseString: unquoted null string"
    END IF

    ' skip trailing spaces and comma
    DO WHILE LEFT$(buf, 1) = " "
        buf = MID$(buf, 2)
    LOOP
    IF LEFT$(buf, 1) = "," THEN
        buf = MID$(buf, 2)
    END IF

    parseString = s
END FUNCTION