The File I/O system automatically maintains a pointer to a position within a file. eg If you read ten characters from a file, the file pointer for that particular file will then be positioned at the eleventh character. Using the FileMovePosition statement, you can reposition the pointer to anywhere in the file.

The HandleItem parameter must be an Equinox variable type Handle and is the handle of the file which was opened with the FileOpen statement. The WhereExpression parameter indicates the position in the file, starting from 1, where the pointer will be located:

• -1 at the end of the file
• 1 at the start of the file
• n at offset n into the file (an unsigned 32-bit value)

The system workarea SysError is set to a non-zero value if an error occurs, otherwise zero.

The first example goes to the end of a random file which is already open and appends a string.

FileMovePosition hTest, -1
FileWrite hTest, "Test 1"

This next example opens a sequential file, writes some records and then writes the number of records at the beginning of the file.

handle hTest
number count(6, 0)

| Open a file and test for error
FileOpen "TEST.DAT", StreamCreate, hTest

if hTest = -1 then

Alert "File Opening Error"
exit method

end if

count = -1
FilePrint hTest, count
Print "Records start at", FilePosition (hTest)

Subtable Items

count = 0
FirstRecord

| Write some records
while not syserror

count += 1
FilePrint hTest, RefNo

nextrecord
end while

| Go Back to the beginning of the File
FileMovePosition hTest, 1

if syserror then

Alert "File Pointer Error"
exit subtable

end if

| Write the number of records
FilePrint hTest, count

end subtable | Items

FileClose hTest