Reading and writing text or binary files
You use PowerScript text file functions to read and write
text in line mode or text mode, or to read and write binary files
in stream mode:
-
In line
mode, you can read a file a line at a time until either
a carriage return or line feed (CR/LF) or the end-of-file
(EOF) is encountered. When writing to the file after the specified
string is written, PowerScript appends a CR/LF. -
In stream mode, you can read
the entire contents of the file, including any CR/LFs.
When writing to the file, you must write out the specified blob (but
not append a CR/LF). -
In text mode, you can read
the entire contents of the file, including any CR/LFs.
When writing to the file, you must write out the specified string (but
not append a CR/LF).
Reading a file into a MultiLineEdit
You can use stream mode to read an entire file into a MultiLineEdit,
and then write it out after it has been modified.
Understanding the position pointer
When PowerBuilder opens a file, it assigns the file a unique
integer and sets the position pointer for the file to the position
you specify—the beginning, after the byte-order mark, if
any, or end of the file. You use the integer to identify the file
when you want to read the file, write to it, or close it. The position
pointer defines where the next read or write will begin. PowerBuilder
advances the pointer automatically after each read or write.
You can also set the position pointer with the FileSeek or FileSeek64 function.
File functions
These are the built-in PowerScript functions that manipulate
files:
|
Function |
Datatype returned |
Action |
|---|---|---|
|
FileClose |
Integer |
Closes the specified file |
|
FileDelete |
Boolean |
Deletes the specified file |
|
FileEncoding |
Encoding enumerated type |
Returns the encoding used in the file |
|
FileExists |
Boolean |
Determines whether the specified file |
|
FileLength |
Long |
Obtains the length of a file with a file |
|
FileLength64 |
LongLong |
Obtains the length of a file of any size |
|
FileOpen |
Integer |
Opens the specified file |
|
FileRead |
Integer |
Reads from the specified file (deprecated) |
|
FileReadEx |
Long |
Reads from the specified file |
|
FileSeek |
Long |
Seeks to a position in a file with a |
|
FileSeek64 |
LongLong |
Seeks to a position in a file of any |
|
FileWrite |
Integer |
Writes to the specified file (deprecated) |
|
FileWriteEx |
Long |
Writes to the specified file |
Encoding
The last argument in the FileOpen function
lets you create an ANSI, UTF-8, UTF-16LE (Little Endian), or UTF16-BE
(Big Endian) file.
The encoding argument, like all arguments
of the FileOpen function except the file name,
is optional. You need only specify it if you want to create a new
text file with Unicode encoding. If the filename argument
refers to a file that does not exist, the FileOpen function
creates the file and sets the character encoding specified in the encoding argument.
By default, if the file does not exist and the encoding argument
is not specified, PowerBuilder opens a file with ANSI encoding.
This ensures compatibility with earlier versions of PowerBuilder.
The FileRead and FileWrite functions
cannot read more than 32,766 bytes at a time. The FileReadEx and FileWriteEx functions
can write an unlimited number of bytes at a time.