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Categories / Delphi / Procedures

 

Writeln - write a complete line of data to a text file system unit

1 procedure WriteLn ( Expression1 {options} {, Expression2 {options} ...} ) ; 2 procedure WriteLn ( var FileHandle : TextFile; Expression1 {options} {, Expression2 {options} ...} ) ; Description The WriteLn procedure writes a complete line of data to a text 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. You must use AssignFile to assign a file to the FileHandle and open the file with Reset or ReWrite before using WriteLn. 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 Notes WriteLn does not buffer records, so performance is degraded. BlockWrite is more efficient, but is geared to writing to binary files. Related commands Append Open a text file to allow appending of text to the end 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 Write Write data to a binary or text file Example code : Illustrating single, multiple and formatted text line writing var myFile : TextFile; text : string; 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 WriteLn(myFile, 'Hello World'); // Write a blank line WriteLn(myFile); // Write a string and a number to the file WriteLn(myFile, '22/7 = ' , 22/7); // Repeat the above, but with number formatting WriteLn(myFile, '22/7 = ' , 22/7:12:6); // Close the file CloseFile(myFile); // Reopen the file for reading 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 22/7 = 3.14285714285714E:0000 22/7 = 3.142857