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codecaine · 02-03-2010, 01:24 PM

Example of piping with unix api using free pascal compiler

Code:

program pipeExample(input,output);

{This example was coded by jerome scott II aka codecaine}

uses

    BaseUnix, unixtype, Unix;

const

BUFF_MAX = 500;

var

    fpIn, fpOut : TFilDes; 

    child : TPid;

    x : Integer;

    buff : Array of char;

    names : Array [1..5] of ANSIString = ('bill','jerome','adam','lewis','mark');

begin

    //set the length of buff

    setLength(buff,BUFF_MAX);

    //create 2 pipes

    FpPipe(fpIn);

    FpPipe(fpOut);

    //create new process

    child := fpFork();

    //check if new process failed

    if child = -1 then

    begin

        writeLn('fork failed');

        exit;

    end;

    //parent child

    if child <> 0 then

    begin

        FpClose(fpIn[0]); //no need to read from pipe

        FpClose(fpOut[1]); //no need to write to pipe

        //loop and write to the pipe

        for x := 1 To 5 do

        begin

            names[x] := names[x] + #10;

            FpWrite( fpIn[1], PChar(names[x]), Length(names[x]));

        end;

        FpClose(fpIn[1]); //close the pipe so let read know it is ok to go

        //read the pipe data back in to the program here you can maniulate the data if you like

        FpRead(fpout[0],buff[0],BUFF_MAX);

        writeln('Result:');

        for x := 0 to length(buff) do

            write(buff[x]);

    end

    else

    begin

        FpClose(fpIn[1]); //no need to write to pipe

        FpClose(fpOut[0]); //no need to read from pipe

        FpDup2(fpIn[0],0);

        FpDup2(fpOut[1],1);

        FpExecLP('sort', []);

    end;

end.

***drdebcol*** · 02-03-2010, 11:50 PM

Great code, same as in C++ setLength() is very good function, i use it for arrays !

***drdebcol*** · 04-08-2010, 04:16 AM

I was skimming through this code and i don't understand this function "fpFork()". What does it do ?

***Back_track*** · 04-08-2010, 07:01 AM

@Drdebcol

Quote:FpFork creates a child process which is a copy of the parent process. FpFork returns the process ID in the parent process, and zero in the child's process. (you can get the parent's PID with fpGetPPid).