freepascal.compiler/docs/linuxex/ex37.pp

Program Example37;

{ Program to demonstrate the Popen function. }

uses linux;

var f : text;
    i : longint;
    
begin
  writeln ('Creating a shell script to which echoes its arguments');
  writeln ('and input back to stdout');
  assign (f,'test21a');
  rewrite (f);
  writeln (f,'#!/bin/sh');
  writeln (f,'echo this is the child speaking.... ');
  writeln (f,'echo got arguments \*"$*"\*');
  writeln (f,'cat');
  writeln (f,'exit 2');
  writeln (f);
  close (f);
  chmod ('test21a',octal (755));
  popen (f,'./test21a arg1 arg2','W');
  rewrite (f);
  if linuxerror<>0 then 
     writeln ('error from POpen : Linuxerror : ', Linuxerror);
  for i:=1 to 10 do 
    writeln (f,'This is written to the pipe, and should appear on stdout.');
  Flush(f);
  Writeln ('The script exited with status : ',PClose (f));
  writeln;
  writeln ('Press <return> to remove shell script.');
  readln;
  assign (f,'test21a');
  erase (f)
end.