| Server-side object | |
| Implemented in | LiveWire 1.0 |
File constructor:new File("path")
path | The path and filename in the format of the server's file system (not a URL path). |
File object to write to or read from a file on the server. For security reasons, you cannot programmatically access the file system of client machines.
You can use the File object to generate persistent HTML or data files without using a database server. Information stored in a file is preserved when the server goes down.
|
Allows the addition of properties to a File object.
|
File object userInfo that refers to a physical file called info.txt. The info.txt file resides in the same directory as the application's .web file:userInfo = new File("info.txt")
Example 2. In the following example, the File object refers to a physical file with an absolute path:userInfo = new File("c:\\data\\info.txt")
Example 3. The following example displays the name of a File object onscreen.userInfo = new File("c:\\data\\info.txt")
write(userInfo)
Function.prototype.
| Property of |
File
|
| Implemented in | LiveWire 1.0 |
| Method of |
File
|
| Static | |
| Implemented in | LiveWire 1.0 |
byteToString(number)
number | A number that represents a byte. |
stringToByte and byteToString methods to convert data between binary and ASCII formats. The byteToString method converts the number argument into a string.
Because byteToString is a static method of File, you always use it as File.byteToString(), rather than as a method of a File object you created.
while loop executes until the pointer is positioned past the end of the file. Inside the loop, the readByte method reads the current character from the source file, and the byteToString method converts it into a string; the write method writes it to the target file. The last readByte method positions the pointer past the end of the file, ending the while loop. See the File object for a description of the pointer.// Create the source File object
source = new File("c:\data\source.txt")
// If the source file opens successfully, create a target file
if (source.open("r")) {
target = new File("c:\data\target.txt")
target.open("w")
// Copy the source file to the targetThis example is similar to the example used for the
while (!source.eof()) {
data = File.byteToString(source.readByte())
target.write(data);
}
source.close()
}
target.close()
write method of File. However, this example reads bytes from the source file and converts them to strings, instead of reading strings from the source file.File.stringToByte
| Method of |
File
|
| Implemented in | LiveWire 1.0 |
clearError()
clearError method clears both the file error status (the value returned by the error method) and the value returned by the eof method.error method.File.error, File.eof
| Method of |
File
|
| Implemented in | LiveWire 1.0 |
close()
close method. If the file is not open, the close method fails. This method returns true if it is successful; otherwise, it returns false.open method.File.open, blob
| Method of |
File
|
| Implemented in | LiveWire 1.0 |
eof()
eof method to determine whether the position of the pointer is beyond the end of a file. See File for a description of the pointer.while loop executes until the pointer is positioned past the end of the file. While the pointer is not positioned past the end of the file, the readln method reads the current line, and the write method displays it. The last readln method positions the pointer past the end of the file, ending the while loop.x = new File("c:\data\userInfo.txt")
if (x.open("r")) {
while (!x.eof()) {
line = x.readln()
write(line+"<br>");
}
x.close();
}
File.getPosition, File.setPosition
| Method of |
File
|
| Implemented in | LiveWire 1.0 |
error()
-1 if the file specified in fileObjectName is not open
error method in an if statement to take different actions depending on whether a call to the open method succeeded. After the if statement completes, the error status is reset with the clearError method.userInput = new File("c:\data\input.txt")
userInput.open("w")
if (userInput.error() == 0) {
fileIsOpen() }
else {
fileIsNotOpen() }
userInput.clearError()
File.clearError
| Method of |
File
|
| Implemented in | LiveWire 1.0 |
exists()
if statement to take different actions depending on whether a physical file exists. If the file exists, the JavaScript runtime engine opens it and calls the writeData function. If the file does not exist, the runtime engine calls the noFile function.dataFile = new File("c:\data\mytest.txt")
if (dataFile.exists() ==true) {
dataFile.open("w")
writeData()
dataFile.close()
}
else {
noFile()
}
| Method of |
File
|
| Implemented in | LiveWire 1.0 |
flush()
File object methods (write, writeByte, or writeln), the data is buffered internally. The flush method writes the buffer to the physical file. The flush method returns true if it is successful; otherwise, it returns false.
Do not confuse the flush method of the File object with the top-level flush function. The flush function flushes a buffer of data and causes it to display in the client browser; the flush method flushes a buffer of data to a physical file.
write method for an example of the flush method.File.write, File.writeByte, File.writeln
| Method of |
File
|
| Implemented in | LiveWire 1.0 |
getLength()
getLength as a counter in a for loop to iterate over every character in the file.// Create the source File object
source = new File("c:\data\source.txt")
// If the source file opens successfully, create a target file
if (source.open("r")) {
target = new File("c:\data\target.txt")
target.open("a")
// Copy the source file to the target
for (var x = 0; x < source.getLength(); x++) {
source.setPosition(x)
data = source.read(1)
target.write(data)
}
source.close()
}
target.close()
| Method of |
File
|
| Implemented in | LiveWire 1.0 |
getPosition()
getPosition method to determine the position of the pointer in a file. See the File object for a description of the pointer. The getPosition method returns the current pointer position; the first byte in a file is byte 0. info.txt, which contains the string "Hello World." The length of info.txt is 11 bytes.
Example 1. In the following example, the first call to getPosition shows that the default pointer position is 0 in a file that is opened for reading. This example also shows that a call to the read method repositions the pointer.
dataFile = new File("c:\data\info.txt")
dataFile.open("r")
write("The position is " + dataFile.getPosition() + "<BR>")
write("The next character is " + dataFile.read(1) + "<BR>")
write("The new position is " + dataFile.getPosition() + "<BR>")
dataFile.close()This example displays the following information:
The position is 0Example 2. This example uses
The next character is H
The new position is 1
setPosition to position the pointer one byte from the end of the eleven-byte file, resulting in a pointer position of offset 10.dataFile = new File("c:\data\info.txt")
dataFile.open("r")
dataFile.setPosition(-1,2)
write("The position is " + dataFile.getPosition() + "<BR>")
write("The next character is " + dataFile.read(1) + "<BR>")
dataFile.close()This example displays the following information:
The position is 10Example 3. You can position the pointer beyond the end of the file and still evaluate
The next character is d
getPosition successfully. However, a call to eof indicates that the pointer is beyond the end of the file.dataFile.setPosition(1,2)This example displays the following information:
write("The position is " + dataFile.getPosition() + "<BR>")
write("The value of eof is " + dataFile.eof() + "<P>")
The position is 12
The value of eof is true
File.eof, File.open, File.setPosition
| Method of |
File
|
| Implemented in | LiveWire 1.0 |
open("mode")
mode | A string specifying whether to open the file to read, write, or append, according to the list below. |
open method to open a file on the server before you read from it or write to it. If the file is already open, the method fails and has no effect. The open method returns true if it is successful; otherwise, it returns false.
The mode parameter is a string that specifies whether to open the file to read, write, or append data. You can optionally use the b parameter anytime you specify the mode. If you do so, the JavaScript runtime engine on the server opens the file as a binary file. If you do not use the b parameter, the runtime engine opens the file as a text file. The b parameter is available only on Windows platforms.
The possible values for mode are as follows:
r[b] opens a file for reading. If the file exists, the method succeeds and returns true; otherwise, the method fails and returns false.w[b] opens a file for writing. If the file does not already exist, it is created; otherwise, it is overwritten. This method always succeeds and returns true.a[b] opens a file for appending (writing at the end of the file). If the file does not already exist, it is created. This method always succeeds and returns true.r+[b] opens a file for reading and writing. If the file exists, the method succeeds and returns true; otherwise, the method fails and returns false. Reading and writing commence at the beginning of the file. When writing, characters at the beginning of the file are overwritten.w+[b] opens a file for reading and writing. If the file does not already exist, it is created; otherwise, it is overwritten. This method always succeeds and returns true.a+[b] opens a file for reading and appending. If the file does not already exist, it is created. This method always succeeds and returns true. Reading and appending commence at the end of the file.close method. info.txt so an application can write information to it. If info.txt does not already exist, the open method creates it; otherwise, the open method overwrites it. The close method closes the file after the writeData function is completed.userInfo = new File("c:\data\info.txt")
userInfo.open("w")
writeData()
userInfo.close()
Example 2. The following example opens a binary file so an application can read data from it. The application uses an if statement to take different actions depending on whether the open statement finds the specified file.entryGraphic = new File("c:\data\splash.gif")
if (entryGraphic.open("rb") == true) {
displayProcedure()
}
else {
errorProcedure()
}
entryGraphic.close()
File.close
| Method of |
File
|
| Implemented in | LiveWire 1.0 |
read(count)
count | An integer specifying the number of characters to read. |
read method reads the specified number of characters from a file, starting from the current position of the pointer. If you attempt to read more characters than the file contains, the method reads as many characters as possible. This method moves the pointer the number of characters specified by the count parameter. See the File object for a description of the pointer.
The read method returns the characters it reads as a string.
info.txt, which contains the string "Hello World." The first read method starts from the beginning of the file and reads the character "H." The second read method starts from offset six and reads the characters "World."dataFile = new File("c:\data\info.txt")
dataFile.open("r")
write("The next character is " + dataFile.read(1) + "<BR>")
dataFile.setPosition(6)
write("The next five characters are " + dataFile.read(5) + "<BR>")
dataFile.close()This example displays the following information:
The next character is H
The next five characters are World
File.readByte, File.readln, File.write
| Method of |
File
|
| Implemented in | LiveWire 1.0 |
readByte()
readByte method reads the next byte from a file, starting from the current position of the pointer. This method moves the pointer one byte. See the File object for a description of the pointer.
The readByte method returns the byte it reads as a number. If the pointer is at the end of the file when you issue readByte, the method returns -1.
You can use the writeByte method to write data read by the readByte method to a file.
while loop executes until the pointer is positioned past the end of the file. While the pointer is not positioned past the end of the file, the readByte method reads the current byte from the source file, and the writeByte method writes it to the target file. The last readByte method positions the pointer past the end of the file, ending the while loop.// Create the source File object
source = new File("c:\data\source.gif")
// If the source file opens successfully, create a target file
if (source.open("rb")) {
target = new File("c:\data\target.gif")
target.open("wb")
// Copy the source file to the target
while (!source.eof()) {
data = source.readByte()
target.writeByte(data);
}
source.close();
}
target.close()
File.read, File.readln, File.writeByte
| Method of |
File
|
| Implemented in | LiveWire 1.0 |
readln()
readln method reads the current line of characters from a file, starting from the current position of the pointer. If you attempt to read more characters than the file contains, the method reads as many characters as possible. This method moves the pointer to the beginning of the next line. See the File object for a description of the pointer.
The readln method returns the characters it reads as a string.
File.eof File.read, File.readByte, File.writeln
| Method of |
File
|
| Implemented in | LiveWire 1.0 |
setPosition(position, reference)
position | An integer indicating where to position the pointer. |
reference | (Optional) An integer that indicates a reference point, according to the list below. |
setPosition method to reposition the pointer in a file. See the File object for a description of the pointer.
The position argument is a positive or negative integer that moves the pointer the specified number of bytes relative to the reference argument. Position 0 represents the beginning of a file. The end of a file is indicated by fileObjectName.getLength().
setPosition method returns true if it is successful; otherwise, it returns false.info.txt, which contains the string "Hello World." The length of info.txt is 11 bytes. The first example moves the pointer from the beginning of the file, and the second example moves the pointer to the same location by navigating relative to the end of the file. Both examples display the following information:The position is 10Example 1. This example moves the pointer from the beginning of the file to offset 10. Because no value for
The next character is d
reference is supplied, the JavaScript runtime engine assumes it is 0.dataFile = new File("c:\data\info.txt")
dataFile.open("r")
dataFile.setPosition(10)
write("The position is " + dataFile.getPosition() + "<BR>")
write("The next character is " + dataFile.read(1) + "<P>")
dataFile.close()Example 2. This example moves the pointer from the end of the file to offset 10.
dataFile = new File("c:\data\info.txt")
dataFile.open("r")
dataFile.setPosition(-1,2)
write("The position is " + dataFile.getPosition() + "<BR>")
write("The next character is " + dataFile.read(1) + "<P>")
dataFile.close()
File.eof, File.getPosition, File.open
| Method of |
File
|
| Static | |
| Implemented in | LiveWire 1.0 |
stringToByte(string)
string | A JavaScript string. |
stringToByte and byteToString methods to convert data between binary and ASCII formats. The stringToByte method converts the first character of its string argument into a number that represents a byte.
Because stringToByte is a static method of File, you always use it as File.stringToByte(), rather than as a method of a File object you created.
stringToByte method is passed "Hello" as an input argument. The method converts the first character, "H," into a numeric value representing a byte.write("The stringToByte value of Hello = " +
File.stringToByte("Hello") + "<BR>")
write("Returning that value to byteToString = " +
File.byteToString(File.stringToByte("Hello")) + "<P>")
The previous example displays the following information:The stringToByte value of Hello = 72
Returning that value to byteToString = H
File.byteToString
| Method of |
File
|
| Implemented in | LiveWire 1.0 |
write(string)
string | A JavaScript string. |
write method writes the string specified as string to the file specified as fileObjectName. This method returns true if it is successful; otherwise, it returns false.
Use the write method to write data to a text file; use the writeByte method to write data to a binary file. You can use the read method to read data from a file to a string for use with the write method.
Do not confuse the write method of the File object with the write function. The write function outputs data to the client browser; the write method outputs data to a physical file on the server.
while loop executes until the pointer is positioned past the end of the file. While the pointer is not positioned past the end of the file, the read method reads the current character from the source file, and the write method writes it to the target file. The last read method positions the pointer past the end of the file, ending the while loop. See the File object for a description of the pointer.// Create the source File object
source = new File("c:\data\source.txt")
// If the source file opens successfully, create a target file
if (source.open("r")) {
target = new File("c:\data\target.txt")
target.open("w")
// Copy the source file to the target
while (!source.eof()) {
data = source.read(1)
target.write(data);
}
source.close();
}
target.flush()
target.close()
File.flush, File.read, File.writeByte, File.writeln
| Method of |
File
|
| Implemented in | LiveWire 1.0 |
writeByte(number)
number | A number that specifies a byte of data. |
writeByte method writes a byte that is specified as number to a file that is specified as fileObjectName. This method returns true if it is successful; otherwise, it returns false.
Use the writeByte method to write data to a binary file; use the write method to write data to a text file. You can use the readByte method to read bytes of data from a file to numeric values for use with the writeByte method.
readByte method.File.flush, File.readByte, File.write, File.writeln
| Method of |
File
|
| Implemented in | LiveWire 1.0 |
writeln(string)
string | A JavaScript string. |
writeln method writes the string specified as string to the file specified as fileObjectName. Each string is followed by the carriage return/line feed character "\n" ("\r\n" on Windows platforms). This method returns true if the write is successful; otherwise, it returns false.
Use the writeln method to write data to a text file; use the writeByte method to write data to a binary file. You can use the readln method to read data from a file to a string for use with the writeln method.
while loop executes until the pointer is positioned past the end of the file. While the pointer is not positioned past the end of the file, the readln method reads the current line from the source file, and the writeln method writes it to the target file. The last readln method positions the pointer past the end of the file, ending the while loop. See the File object for a description of the pointer.// Create the source File object
source = new File("c:\data\source.txt")
// If the source file opens successfully, create a target file
if (source.open("r")) {
target = new File("c:\data\target.txt")
target.open("w")
// Copy the source file to the targetNote that the
while (!source.eof()) {
data = source.readln()
target.writeln(data);
}
source.close();
}
target.close()
readln method ignores the carriage return/line feed characters when it reads a line from a file. The writeln method appends these characters to the string that it writes.File.flush, File.readln, File.write, File.writeByte
Last Updated: 10/31/97 16:37:22