Mega Code Archive
Write - write data to a binary or text file system unit
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1 procedure Write ( Expression1 {options} {, Expression2 {options} ...} ) ;
2 procedure Write ( var FileHandle : TextFile; Expression1 {options} {, Expression2 {options} ...} ) ;
3 procedure Write ( var FileHandle : File; var Value1 {,var Value2 ...} ) ;
Description
The Write procedure writes a single line of data to a file or to the console.
Version 1
Is used to write a line of text to the console.
Version 2
Is used to write a line of text to a text file with the given FileHandle.
Version 3
Is used to write a line of data to a binary file with the given FileHandle.
You must use AssignFile to assign a file to the FileHandle and open the file with Reset or ReWrite before using Write.
For text files, the text written may be any valid Expression(s). Often these will be strings, but may also be expressions that result in strings or numbers.
After each expression, you can add formatting options:
:width Field width for strings + numbers
:precision Decimal digits for numbers
For typed binary files, data values Value1, Value2 etc, are written as data lines to the file. These values must be of the same type as the file.
Notes
You cannot use Write to write to an untyped binary file (one declared as File with no following of type).
To write to a binary file, use BlockWrite.
Write does not buffer records, so it is more efficient to use BlockWrite.
Write is also a Delphi directive. It is used with the Property keyword.
Related commands
AssignFile Assigns a file handle to a binary or text file
BlockRead Reads a block of data records from an untyped binary file
BlockWrite Writes a block of data records to an untyped binary file
File Defines a typed or untyped file
Read Read data from a binary or text file
ReadLn Read a complete line of data from a text file
Reset Open a text file for reading, or binary file for read/write
ReWrite Open a text or binary file for write access
TextFile Declares a file type for storing lines of text
WriteLn Write a complete line of data to a text file
Example code : Illustrating single, multiple and formatted text line writing
var
myFile : TextFile;
text : string;
i : Integer;
begin
// Try to open the Test.txt file for writing to
AssignFile(myFile, 'Test.txt');
ReWrite(myFile);
// Write a couple of well known words to this file
Write(myFile, 'Hello ');
Write(myFile, 'World');
// Terminate this line
WriteLn(myFile);
// Write some numbers to the file as a single line
for i := 2 to 4 do
Write(myFile, i/2, ' ');
// Terminate this line
WriteLn(myFile);
// Repeat the above, but with number formatting
for i := 2 to 4 do
Write(myFile, i/2:5:1);
// Terminate this line
WriteLn(myFile);
// Close the file
CloseFile(myFile);
// Reopen the file for reading only
Reset(myFile);
// Display the file contents
while not Eof(myFile) do
begin
ReadLn(myFile, text);
ShowMessage(text);
end;
// Close the file for the last time
CloseFile(myFile);
end;
Show full unit code
Hello World
1.00000000000000E+0000 1.50000000000000E+0000 2.00000000000000E+0000
1.0 1.5 2.0
Example code : Write typed records to a record type binary file
type
TCustomer = record
name : string[20];
age : Integer;
male : Boolean;
end;
var
myFile : File of TCustomer; // A file of customer record
customer : TCustomer;
begin
// Try to open the Test.cus binary file for writing to
AssignFile(myFile, 'Test.cus');
ReWrite(myFile);
// Write a couple of customer records to the file
customer.name := 'Fred Bloggs';
customer.age := 21;
customer.male := true;
Write(myFile, customer);
customer.name := 'Jane Turner';
customer.age := 45;
customer.male := false;
Write(myFile, customer);
// Close the file
CloseFile(myFile);
// Reopen the file in read only mode
FileMode := fmOpenRead;
Reset(myFile);
// Display the file contents
while not Eof(myFile) do
begin
Read(myFile, customer);
if customer.male
then ShowMessage('Man with name '+customer.name+
' is '+IntToStr(customer.age))
else ShowMessage('Lady with name '+customer.name+
' is '+IntToStr(customer.age));
end;
// Close the file for the last time
CloseFile(myFile);
end;
Show full unit code
Man with name Fred Bloggs is 21
Lady with name Jane Turner is 45
Example code : Writing to a Word type binary file
var
myWord, myWord1, myWord2 : Word;
myFile : File of Word;
begin
// Try to open the Test.bin binary file for writing to
AssignFile(myFile, 'Test.bin');
ReWrite(myFile);
// Write a couple of lines of Word data to the file
myWord1 := 234;
myWord2 := 567;
Write(myFile, myWord1, myWord2);
// Close the file
CloseFile(myFile);
// Reopen the file in read only mode
FileMode := fmOpenRead;
Reset(myFile);
// Display the file contents
while not Eof(myFile) do
begin
Read(myFile, myWord);
ShowMessage(IntToStr(myWord));
end;
// Close the file for the last time
CloseFile(myFile);
end;
Show full unit code
234
567
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