fSeek (Example)

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Example: Retrieving the current position in an external file
Example: Modifying the current position in an external file
Example: Positioning in an external file from the end of file
Example: Retrieving the current position in an external file (WEBDEV)
Example: Modifying the current position in an external file (WEBDEV)

fSeek (Example)

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Example: Retrieving the current position in an external file

The following code is used to retrieve the current position in an external file after reading a block of bytes. The text file is opened in read/write. The name and the path of the text file are selected by fSelect.

// Declare the variables
FileNameAndPath is string
FileID is int
ResRead is string
ResPosition is int
ResCloseFile is int

// Select the file name and path
FileNameAndPath = fSelect("", "", "Selecting an external file", ...
"External file" + TAB + "*.txt", "txt", fselCreate)
// Open file
FileID = fOpen(FileNameAndPath, foReadWrite)
// Display an error message if the opening was not performed
IF FileID = -1 THEN
Error(ErrorInfo(errMessage))
ELSE
// Read the first 1000 bytes in the file
ResRead = fRead(FileID, 1000)
// Display an error message if the reading was not performed
IF ResRead = "" THEN
Error(ErrorInfo(errMessage))
ELSE
// Current position?
ResPosition = fSeek(FileID, 0, fpCurrent)
// Display the position of the pointer
IF ResPosition <> -1 THEN
Info("The current position is:" + ResPosition)
ELSE
// Display the error message if a problem occurred with fSeek
Error(ErrorInfo(errMessage))
END
END
// Close the file
ResCloseFile = fClose(FileID)
IF ResCloseFile = -1 THEN
// Display an error message if the closing was not performed
Error(ErrorInfo(errMessage))
END
END

Example: Modifying the current position in an external file

The following code is used to write a character string from the current position. The text file is opened in read/write. The name and the path of the text file are selected by fSelect.

// Declare the variables
FileNameAndPath is string
FileID is int
ResPosition is int
SizeWritten is int
ResCloseFile is int

// Select the file name and path
FileNameAndPath = fSelect("", "", "Selecting an external file", ...
"External file" + TAB + "*.txt", "txt", fselCreate)
// Open file
FileID = fOpen(FileNameAndPath, foReadWrite)
// Display an error message if the opening was not performed
IF FileID = -1 THEN
Error(ErrorInfo(errMessage))
ELSE
// Position on byte 150
ResPosition = fSeek(FileID, 150, fpBeginning)
IF ResPosition = -1 THEN
// Display an error message if the positioning was not performed
Error(ErrorInfo(errMessage))
ELSE
// Write the character string from the current position
SizeWritten = fWrite(FileID, "Sales progression")
// Display an error message if the writing was not performed
IF SizeWritten = -1 THEN Error(ErrorInfo(errMessage))
END
// Close the file
ResCloseFile = fClose(FileID)
IF ResCloseFile = -1 THEN
// Display an error message if the closing was not performed
Error(ErrorInfo(errMessage))
END
END

Example: Positioning in an external file from the end of file

The following code is used to point to the 100th byte from the end of the file.

// Declare the variables
FilePosition is int // Current position in the file
FileName is string // Name of the test file
FileNum is int = 0 // identifier used to handle the test file

// Select the file name and path
FileName = fSelect("", "", "Selecting an external file", ...
"External file" + TAB + "*.txt" , "txt", fselCreate)
// Open the file in read-only
FileNum = fOpen(FileName, foRead)
// Check the opening of the test file
IF FileNum = -1 THEN
// An error occurred while opening the file
Error("Error while opening the file" + ...
FileName, ErrorInfo())
RETURN
ELSE
// Position from the end
FilePosition = fSeek(FileNum, -100, fpEnd)
IF FilePosition <> -1 THEN
// Read 20 characters from the current position
Info(fRead(FileNum, 20))
ELSE
Info(ErrorInfo())
END
// Close the file
fClose(FileNum)
END

Example: Retrieving the current position in an external file (WEBDEV)

The following code is used to retrieve the current position in an external file after reading a block of bytes. The text file is opened in read/write.

// Declare the variables
FileNameAndPath is string
FileID is int
ResRead is string
ResPosition is int
ResCloseFile is int

// Select the file name and path
FileNameAndPath = "C:\MyDirectories\File.txt"
// Open file
FileID = fOpen(FileNameAndPath, foReadWrite)
// Display an error message if the opening was not performed
IF FileID = -1 THEN
Error(ErrorInfo(errMessage))
ELSE
// Read the first 1000 bytes in the file
ResRead = fRead(FileID, 1000)
// Display an error message if the reading was not performed
IF ResRead = "" THEN
Error(ErrorInfo(errMessage))
ELSE
// Current position?
ResPosition = fSeek(FileID, 0, fpCurrent)
// Display the position of the pointer
IF ResPosition <> -1 THEN
Info("The current position is: " + ResPosition)
ELSE
// Display the error message if a problem occurred with fSeek
Error(ErrorInfo(errMessage))
END
END
// Close the file
ResCloseFile = fClose(FileID)
IF ResCloseFile = -1 THEN
// Display an error message if the closing was not performed
Error(ErrorInfo(errMessage))
END
END

Example: Modifying the current position in an external file (WEBDEV)

The following code is used to write a character string from the current position. The text file is opened in read/write.

// Declare the variables
FileNameAndPath is string
FileID is int
ResPosition is int
SizeWritten is int
ResCloseFile is int

// Select the file name and path
FileNameAndPath = "C:\MyDirectories\File.txt"
// Open file
FileID = fOpen(FileNameAndPath, foReadWrite)
// Display an error message if the opening was not performed
IF FileID = -1 THEN
Error(ErrorInfo(errMessage))
ELSE
// Position on byte 150
ResPosition = fSeek(FileID, 150, fpBeginning)
IF ResPosition = -1 THEN
// Display an error message if the positioning was not performed
Error(ErrorInfo(errMessage))
ELSE
// Write the character string from the current position
SizeWritten = fWrite(FileID, "Sales progression")
// Display an error message if the writing was not performed
IF SizeWritten = -1 THEN Error(ErrorInfo(errMessage))
END
// Close the file
ResCloseFile = fClose(FileID)
IF ResCloseFile = -1 THEN
// Display an error message if the closing was not performed
Error(ErrorInfo(errMessage))
END
END