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Boost.Process.md

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TPipe

The TPipe implement a class for easy manager command line aplications and redirect child process I/O.

Features

  • Run child process;
  • Write WideString, AnsiString and bytes on child;
  • Read all data from child process (just after close it);
  • Wait for child process close;
  • Force close;

Methods

	constructor Create; overload;
	constructor Create(CommandLine: string); overload;
	destructor Destroy; override;

Constructors for TPipe, support:

  • No parameter constructor: For run application in future (use "Run" method to run);
  • CommandLine(String): Create a object and run the command line;
	procedure Write(const Buffer; Size: DWord); overload;

Generic function to write data in child process

Params:

  • Buffer: Any data variable (string, array, variable etc.);
  • Size(DWord): Size of data buffer in bytes;

Return:

  • None;

Example:

procedure Main;
var 
	Pipe: TPipe;
	intValue:Integer;
begin	
	intValue := 1500;
	Pipe: TPipe.Create("ChildProcess.exe");	
	
	// Write 1500 on ChildProcess.exe
	Pipe.Write(intValue, SizeOf(Integer));

	// Wait until ChildProcess.exe terminate
	Pipe.Wait;

	// Read ChildProcess.exe content text (or error)
	Pipe.ReadAllData;
	Pipe.free;
end;
	procedure Write(value: string); overload;
	procedure WriteA(value: AnsiString); overload;

Function to write string in child process. The "WriteA" is for write a AnsiString;

Params:

  • value(string for Write): WideString to write in child process;
  • value(AnsiString for WriteA): AnsiString to write in child process;

Return:

  • None;
	procedure Write(FmtString: string; Params: array of const); overload;	
	procedure WriteA(FmtString: AnsiString; Params: array of const); overload;

Function to write string formated in child process. The "WriteA" is for write a AnsiString;

Params:

  • FmtString(string for Write): WideString format to write in child process;
  • FmtString(AnsiString for WriteA): AnsiString format to write in child process;
  • Params(array of const): Any data variable or const to write.

Return:

  • None;

Example:

procedure Main;
var 
	Pipe: TPipe;
begin		
	Pipe: TPipe.Create("ChildProcess.exe");	
	
	// Write "hello world" (WideString) in ChildProcess.exe
	Pipe.Write('hello world');

	// Write "hello world" (AnsiString) in ChildProcess.exe
	Pipe.WriteA('hello world');

	// Write "1 0xF 3.14" (WideString) in ChildProcess.exe
	Pipe.Write('%d 0x%x %f',[ 2, 15, 3.14]);

	// Write "1 0xF 3.14" (AnsiString) in ChildProcess.exe
	Pipe.WriteA('%d 0x%x %f',[ 2, 15, 3.14]);

	// Wait until ChildProcess.exe terminate
	Pipe.Wait;

	// Read ChildProcess.exe content text (or error)
	Pipe.ReadAllData;
	Pipe.free;
end;
	procedure Write(value: byte); overload;

Function to write a single byte in child process.

Params:

  • value(byte): byte to write in child process;

Return:

  • None;
	procedure Write(value: AnsiChar); overload;

Function to write a single char (ansi, 0..255) in child process.

Params:

  • value(AnsiChar): char to write in child process;

Return:

  • None;
	procedure Write(value: DWORD); overload;

Function to write a DWORD (cardinal) value in child process.

Params:

  • value(DWORD): value to write in child process;

Return:

  • None;

Example:

procedure Main;
var 
	Pipe: TPipe;
begin		
	Pipe: TPipe.Create("ChildProcess.exe");	
	
	// Write 0xFF byte in ChildProcess.exe
	Pipe.Write($FF);

	// Write #32 char in ChildProcess.exe
	Pipe.Write(#32);

	// Write 1500 (unsigned) in ChildProcess.exe
	Pipe.Write(1500);

	// Wait until ChildProcess.exe terminate
	Pipe.Wait;

	// Read ChildProcess.exe content text (or error)
	Pipe.ReadAllData;
	Pipe.free;
end;
	function ReadAllData(Func: TProc<string> = nil): string;

Function to read text from child process after it close (this function blocking and will wait for it close).

Params:

  • Func(TProc): This function is a callback from pipe, this is usefull for interate with other applications, read strings outputs like progress. It can be omited, in this case, all string data can be read in return of function, when the other application close. Tip: If use ReadAllData in Vcl application is recomend use Application.ProcessMessages inside Func, this can reduce hung up of application, but this no work if the other appplication no update your status by using sdout messages.

Return:

  • Result(string): Text from child process;

Example:

procedure Log(data: string);
begin
  Savlog(data); // SavLog is a function to store in disk
  Application.ProcessMessages; // Reduce hung up
end;

procedure TForm1.btn1Click(Sender: TObject);
begin
  p := TPipe.Create('youtube-dl -f 22 "https://youtu.be/cRWWzd_yaig"'); // Create and run youtube-dl

  mmo1.Text := p.ReadAllData(Log); // Read all strings data and save in memo
  p.Free;
end;

Note: Youtube-dl can be found at.

This is the output of log:

[25/01/2021 11:49:45]  [youtube] cRWWzd_yaig: Downloading webpage

[25/01/2021 11:49:46]  [download] Destination: Introducing RAD Studio 10.4 Sydney-cRWWzd_yaig.mp4

[25/01/2021 11:49:46]  
[download]   0.0% of 14.92MiB at Unknown speed ETA Unknown ETA
[download]   0.0% of 14.92MiB at Unknown speed ETA Unknown ETA
[25/01/2021 11:49:46]  
[download]   0.0% of 14.92MiB at 509.69KiB/s ETA 00:29        
[download]   0.0% of 14.92MiB at Unknown speed ETA Unknown ETA
[25/01/2021 11:49:46]  
[download]   0.1% of 14.92MiB at  1.07MiB/s ETA 00:13         
[download]   0.0% of 14.92MiB at Unknown speed ETA Unknown ETA
[25/01/2021 11:49:46]  
[download]   0.2% of 14.92MiB at  1.71MiB/s ETA 00:08         
[download]   0.0% of 14.92MiB at Unknown speed ETA Unknown ETA
[25/01/2021 11:49:46]  
[download]   0.4% of 14.92MiB at  2.27MiB/s ETA 00:06         
[download]   0.8% of 14.92MiB at  2.87MiB/s ETA 00:05         
[25/01/2021 11:49:46]  
[download]   1.7% of 14.92MiB at  2.89MiB/s ETA 00:05         
[download]   0.8% of 14.92MiB at  2.87MiB/s ETA 00:05         
[25/01/2021 11:49:46]  
[download]   3.3% of 14.92MiB at  4.58MiB/s ETA 00:03         
[download]   0.8% of 14.92MiB at  2.87MiB/s ETA 00:05         
[25/01/2021 11:49:46]  
[download]   6.7% of 14.92MiB at  6.52MiB/s ETA 00:02         
[download]   0.8% of 14.92MiB at  2.87MiB/s ETA 00:05         
[25/01/2021 11:49:46]  
[download]  13.4% of 14.92MiB at  8.23MiB/s ETA 00:01         
[download]   0.8% of 14.92MiB at  2.87MiB/s ETA 00:05         
[25/01/2021 11:49:47]  
[download]  26.8% of 14.92MiB at  9.47MiB/s ETA 00:01         
[download]   0.8% of 14.92MiB at  2.87MiB/s ETA 00:05         
[25/01/2021 11:49:47]  
[download]  53.6% of 14.92MiB at 10.27MiB/s ETA 00:00         
[download]   0.8% of 14.92MiB at  2.87MiB/s ETA 00:05         
[25/01/2021 11:49:47]  
[download]  80.4% of 14.92MiB at 10.58MiB/s ETA 00:00         
[download]   0.8% of 14.92MiB at  2.87MiB/s ETA 00:05         
[25/01/2021 11:49:48]  
[download] 100.0% of 14.92MiB at 10.72MiB/s ETA 00:00         
[download]   0.8% of 14.92MiB at  2.87MiB/s ETA 00:05         
[25/01/2021 11:49:48]  
[download] 100% of 14.92MiB in 00:02                          
[download]   0.8% of 14.92MiB at  2.87MiB/s ETA 00:05         

	function Wait(Ms: DWord = INFINITE): boolean;

Function to read text from child process after it close (this function blocking and will wait for it close).

Params:

  • Ms(DWord): Wait milliseconds until program close. DEFAULT: INFINITE = max Dword;

Return:

  • Result(boolean): Return True if child process closed sucessfull before timeout. False if timout or closed by error;
	function Kill: boolean;

Function to force close child process;

Params:

  • None;

Return:

  • Result(boolean): Return True if child process closed sucessfull otherwise return False;

Example:

procedure Main;
var 
	Pipe: TPipe;
begin		
	Pipe: TPipe.Create("ChildProcess.exe");	

	// Wait for 1s to ChildProcess.exe terminate, if not close it
	if not Pipe.Wait(1000) then
		Pipe.Kill;

	// Read ChildProcess.exe content text (or error)
	Pipe.ReadAllData;
	Pipe.free;
end;